welcome to bbc news, broadcasting to viewers in north america and around the globe. i'm gavin grey. our top stories: the uk's terror threat level is raised as the hunt goes on for the person who planted a bomb on a rush—hour train in london. the joint terrorism analysis centre, the independent organisation responsible for setting the threat level on the basis of available intelligence, has now decided to raise the national threat level from severe to critical. it's the fifth terror attack in the uk this year. the so—called islamic state group says it planted the device which injured 29 people. north korea's leader says his country will meet its nuclear ambitions despite sanctions, after the un strongly condemned friday's missile test. and the cassini space probe plunges into saturn, ending a 13—yearjourney of groundbreaking discoveries. the uk terror threat has been

increased to critical, the highest level, meaning an attack may be imminent. it's in the wake of a bomb explosion on a rush—hour train in london. british police say they are treating the explosion as a terrorist incident. 29 people were injured. so—called islamic state says it carried out the attack. it happened at the height of the morning rush hour as a train pulled into the station at parsons green in south—west london. the bbc understands that the bomb, described as a homemade device, had been fitted with a timer, but it failed to fully detonate. whoever planted it is still on the run. the first of our reports is from our special correspondent lucy manning. on the floor of the tube, still in flames, it was supposed

to blow up the carriage. that bag is on fire. it caused panic, fear, some injuries, but thankfully it didn't kill. guys, let's get away and move to the end of the platform. at 8:20am, this train, packed with commuters, had just arrived at parsons green. it was loud enough to make me wonder what the bang was, and i looked round and this wall of fire was just coming towards us. i turned left and i saw the fireball surge towards my side. luke walmsley was in the carriage listening to music. a bang and then a flash to my left. almost immediately, sort of a surge of people screaming and running towards me. the improvised bomb was in a white bucket, with wires attached, in a lidl freezer bag. within minutes, armed police, fire crews and ambulances arrived. it was clear there

were some injuries. no—one allowed through here, yeah? burns and, from the stampede after, nearly 30 taken to hospital. this woman's commute to work ending in a very different way. relieved to be safe. a large area around parsons green tube station has been cordoned off and this afternoon the police announced they were evacuating local residents living closest to it, to allow them to try and make that device left on the train a bit more stable. as so—called islamic state said it carried out this terror attack, the police hunted the would—be bomber and the terror threat level to the uk was raised. the joint terrorism analysis centre, the independent organisation which is responsible for setting the threat level on the basis of available intelligence, has now decided to raise the national threat level

from severe to critical. this means that their assessment is that a further attack may be imminent. the army will now replace police officers at some locations, as hundreds of detectives search for who planted this bomb. this is a very complex investigation which is continuing at speed with the full weight of the london counterterrorism policing resources assisted by colleagues from around the country and our intelligence agency partners, such as mi5. for those who walked out of the tube carriage today, there is, of course, relief. but with a bomber on the run and fears that another attack could be imminent, these are tense times for those whose job it is to catch him. lucy manning, bbc news, parsons green. the bomb is being examined by forensic teams and officers are looking through cctv at the station for clues about who planted it.

our security correspondent gordon corera reports. the device at the heart of the investigation. the ongoing hunt for the person who planted it has now led to the uk's threat level moving up to critical — its highest level. the makeshift bomb will have yielded some clues in that hunt. like these wires coming from the bucket, used to try and trigger an explosion. they look similar to these christmas tree lights that a birmingham man planned to use in a home—made device before he was arrested. such improvised devices do not always go off properly. that was the case on july 21st, 2005. experts believe today's bomb also didn't explode as intended. the size of the device that was employed was quite significant. and had that device functioned in its intended and designed mode, we'd have seen considerable casualties. many people injured and probably

many people killed. the explosive may have been a compound called tatp. this footage from brussels airport and metro shows the devastation when it detonates properly, more than 30 were killed. it's also thought to have been used in the manchester arena attack this year. that involved a suicide bomber. but today's attacker wanted to get away and used a timer. that is similar to damon smith, seen here leaving a timed device at north greenwich a year ago, which was spotted before it went off. today, hundreds of counterterrorism detectives have been deployed in this investigation. they've been forensically analysing this device, looking for fingerprints and dna. they've also been scouring cctv images, looking for an individual carrying this bag onto the tube and then getting off without it. that will have been the starting point for their manhunt. mi5 are helping the investigation.

they will want to know if the individual was part of a group or acted alone and, as has often been the case recently, if they were previously known to authorities. unfortunately it would not be a surprise and this concept of a lone wolf now would more accurately be described as a known wolf. increasingly attacks, when they happen, have been committed by individuals who were known in some way to either the counterterrorism police or mi5 beforehand. 0fficials here have reacted with irritation to this tweet from donald trump: theresa may responded that it was never helpful to speculate about an ongoing investigation. for the fifth time this year, the country is dealing

with the aftermath of a terrorist attack. and tonight, with no sign yet of an arrest, officials felt they had to raise the threat level amid fears the danger has not yet passed. you can keep up—to—date with the manhunt in london, following the parsons green attack, by going to our website where there is also more eyewitness accounts and analysis. just click on our website bbc.com/news or download the bbc news app. let's take a look at some of the other stories the united nations security council has again condemned north korea for carrying out what it called a "highly provocative" missile test on friday. however, there was no mention in the un statement of any further sanctions. the north korean leader, kim jong—un, has announced that his country's nuclear programmes will continue, despite sanctions, in order to have an "equilibrium" with the united states.

bill hayton reports. north korea is celebrating, another successful test for its hwasong—i2 ballistic missile, and kim jong—un was there to congratulate the scientists. he told them it was his aim to establish a "balance of force" with the united states, so it cannot threaten his country with military action. but on a visit to an airbase near washington, president trump said the us would never be intimidated. after seeing your capabilities and commitment here today, i am more confident than ever that our options in addressing this threat are both effective and overwhelming. in new york, the un security council discussed the situation for the second time this week. this time, there was no new resolution, only a press statement strongly condemning the missile launch, and urging compliance with existing sanctions.

and russia says the us has to get serious about talks with north korea. we called on our us partners and others, to implement political and diplomatic solutions that are provided for in the resolution, and without implementing this we also will consider it as non—compliance with the resolution, not fully implementing the resolution. but as russia and china urged patience, the us says it is running out of time. it wants an end to north korea's missile and nuclear programmes, but with those programmes making rapid progress, the choices facing world leaders are becoming more difficult. joining me now is daniel sneider, a visiting scholar at the shorenstein asia—pacific research centre at stanford thank you forjoining us. you have

been working on research focusing on current us foreign and national security policy in asia. here we go again, iam security policy in asia. here we go again, i am tempted to say with another missile firing, and with more words. that's right. it is a pretty clear pattern that the north koreans behaviour is well established, they are going to respond to every step taken against them with an act of defiance, and they will move down the road that they are on technically, because i think you have to see these tests, not only as a political statement but also as a test of capability. in this case, a range ofan test of capability. in this case, a range of an intermediate range politically style that can reach guam and other us bases, and they wa nt to guam and other us bases, and they want to demonstrate that they can do that. is it your opinion that the sanctions are not working and however strict they get, they will not work? it depends on the goal. sanctions can work to cut back the

goal of hard —— flow of hard currency into north korea, which makes it difficult to have guns and butter, but it will not convert the goal of getting them to the negotiating table to give up those nuclear weapons and even restrict them. we have to be real stick about what they can accomplish, and even this case the last of those sanctions were pretty marginal in character. often in these situations there is talk of negotiations being done by back channels. the think there are no back channels with negotiations under way, or do you think you would like to see them england anyway? there are those kinds of contacts going on, to my knowledge. in fact there was a meeting with the north koreans in switzerland earlier this week, and i gather from people who were present at that meeting, the north koreans we re at that meeting, the north koreans were ina at that meeting, the north koreans were in a pretty feisty mood, not indicating that they are ready to talk. but i think most people that i know believe that the north koreans

are hardly ruling out negotiations, in fact they are trying to position themselves to direct negotiations with the united states, not with eve ryo ne with the united states, not with everyone else, i do think they want to be ina everyone else, i do think they want to be in a room again with the chinese, and they certainly don't wa nt to chinese, and they certainly don't want to be in a room with the south koreans. i don't rule out talks, and i think the north koreans want to enter such talks, if they take place with maximum leveraged and with what they view as a position of strength, and friendly they are getting there. thank you for the analysis. still to come on bbc news, concerns grow about in egyptian lawyer detained as he was about to fly to switzerland to meet with human rights activists. freedom itself was attacked this morning, and freedom will be defended. the united states will hunt down and punish those responsible. bishop tutu now becomes spiritual leader of 100,000 anglicans here — of the blacks in soweto township,

as well as the whites, in their rich suburbs. we say to you today, in a loud and a clear voice, enough of blood and tears — enough! translation: the difficult decision we reached together was one that required great and exceptional courage. it's an exodus of up to 60,000 people, caused by the uneven pace of political change in eastern europe. iam free! this is bbc news. the latest headlines: the terror threat level in the uk is raised after an explosion hits a morning

rush—hour commuter train in london. north korea's leader, kimjong—un, has said his country will meet its nuclear ambitions despite sanctions, after the un strongly condemns friday's missile test. united nations human rights experts are extremely worried about the arrest of an egyptian lawyer who was detained as he was about to fly to switzerland to meet them. the lawyer, ibrahim metwaly, was due to speak to the un working group on enforced disappearances about cases including that of giulio regeni, the italian doctoral student who was tortured to death in egypt. from cairo, 0rla guerin reports. lawyer ibrahim metwaly, who dared to fight for egypt's disappeared, including his eldest son, amr. last sunday, at cairo airport, he disappeared himself. he wound up here at the high—security tora prison complex, instead of addressing

un experts in geneva. now, the lawyer is facing charges of illegally founding an organisation for families of the disappeared. his younger son abdel moneim, also a campaigner, told me he knew the risks, but he wanted to speak for the disappeared, like the murdered italian giulio regeni. translation: my father actually expected that he might be stopped at the airport, but he chose not to let fear control him. he took the risk to bring the voice of the victims, to the un, and the entire world. your brother has disappeared, your father is now behind bars. are you worried that you could be next? translation: i am living with this fear. it's difficult, but history will remember that i did something. human rights groups say as many

as 1,300 people have disappeared off the streets in egypt over the past two years, taken by the military or national security agencies. they say most reappear weeks or months later, in custody, having been tortured. last year, the italian researcher giulio regeni was tortured to death after he vanished in cairo. egyptian authorities denied involvement, but rome recalled its ambassador. though there has been nojustice for regeni, a new italian ambassador has just arrived here. human rights campaigners say that sends the wrong message to the egyptian government. it has already emboldened them, just by announcing that the ambassador is coming back to egypt. we had a website blocked,

we had members arrested, and more and more, the government feels entitled to do whatever it wants. how serious could the consequences be? i think the plan for the government is to silence anybody who speaks out on enforced disappearances. we asked egypt's interior ministry for an interview or comment about forced disappearances. it didn't respond. but, in the past, the ministry has said there is no such thing in egypt, not a single case, and any allegations to the contrary are part of a propaganda campaign against the government. after 20 years in space, the cassini mission to saturn has come to a spectacular end. the probe had run out of fuel, and the us space agency, nasa, had commanded it to destroy itself by plunging into the planet's atmosphere. 0ur science editor david shukman has more. it has been a journey that sounds like something from science fiction,

nasa conjuring up animations of the cassini spacecraft flying around the spectacular rings of saturn. but this really did happen, and these are some of the images the mission actually captured. the planet seen from closer than ever before. the strange detail of its rings. a jetstream in the shape of a hexagon. and an utterly weird collection of moons. but today, the expedition had to come to an end. i'm going to call this the end of mission. at mission control, in california, hugs and applause. for many, it has been the work of a lifetime, and no surprise there were very mixed feelings as the final signal reached earth. well, it's been a part of my life for 20 years. we've spent day in and day out thinking about cassini, planning the observations, focusing on the science. my career has been based on cassini,

so it's really hard to see that go. saturn is the most distant world to have been explored for so long. and the cassini spacecraft, which is almost as big as a bus, has achieved something never attempted before. it has given us unprecedented views, and these have led to dozens of discoveries. the mission is described as one of the most remarkable journeys of exploration, while it has been orbiting saturn for a staggering 13 years. now, it is one of saturn's moons, called enceladus, that has produced the most startling revelation. plumes of vapour were spotted blasting out of it. now, this turned out to be water. so let's take a closer look inside what we now know, that under a covering of ice, there is an ocean. and scientists have come to an amazing conclusion —

that in here there is every ingredient needed for life. this opens up a whole new realm of possibilities in the search for life beyond earth. and the discovery of conditions on moons like enceladus is a real breakthrough for scientists like linda spilker, who started her career at nasa three decades ago, when the mission began. we wanted to know, is there life on enceladus's ocean? could there be oceans inside of other moons? it will take future missions to go back and answer those questions. the mission captured these images of saturn's moon titan, and this is the sound the spacecraft recorded. to make sure cassini didn't contaminate any of the worlds where there may be life, it was sent to its destruction. but it has raised some tantalising new questions. david shukman, bbc news. finishing touches are being made to the largest museum of african contemporary art, which is about to open in cape town. boasting 80 galleries spread over nine floors, the zeitz museum of contemporary art africa has been transformed from an abandoned grain silo.

0ur arts editor will gompertz has been to see it. table mountain, one of cape town's iconic sites, along with the city's spectacular coastline, and the victoria and alfred waterfront, which now boasts a brand—new attraction, the zeitz museum of contemporary african art, which has been created by repurposing the harbour‘s imposing, long—redundant concrete grain silos. there was this extraordinary pair of buildings made from tubes. and it felt that its tube—iness was the thing that could be its spirit and character. we realised the tubes could offer us this opportunity, if we carved a major space out of them, and didn't fight them, but enjoyed them, it made this unusual thing. he says his 80—gallery building is the biggest art museum to be opened in africa for over a century,

and dedicated to showing contemporary african art, the majority of which is owned by this german businessman, who has his name above the door. we wanted to be as representative as possible of africa as a whole, which obviously is incredibly diverse. 5a countries, a huge continent. and there's only so much you can collect. our goal was always to just create a platform. and it's not us talking, but having the artists talk about africa. because, for us, it is important that africa writes its own history, and its own future. we're just there to facilitate and help in exciting journey. some think the zeitz mocaa has got it right. others think it represents a partial, largely white, male view of the african art scene. either way, there is a general agreement that the new museum is a significant and timely addition to the continent's cultural landscape. we now have a space that is, quote—unquote, "of an international

standard", where we can have our work housed. it gives a clear understanding of the fact that we can operate on the same level as places like the guggenheim, or the tate. uh...yeah, it's an important moment for us. for those artists exhibiting in this museum, or the many other gallery spaces popping up in this city and beyond, this is definitely a moment. the world is paying attention. they have a voice. the energy is here. in fact, it is quite possible that they will become the new international avant garde. will gompertz, bbc news, cape town. the cult american actor harry dean stanton has died at the age of 91. in a career that lasted over 60 years, stanton appeared in films including paris,texas, cool hand luke, alien, and godfather ii. he was notable for his hangdog features, and often played loners and offbeat characters. he was also a talented musician, playing guitar and harmonica, and singing with a tenor voice. he served in the us navy in the second world war, and fought in the battle of okinawa. his agent said he died peacefully at cedars—sinai hospital in los angeles. a reminder of our top story: the uk

terror threat has been raised to critical, the highest level, following the london tube bombing during the morning rush hour. it means a further attack may be imminent. it is thought the device didn't detonate as intended. 29 people were injured. hundreds of detectives are searching for the perpetrators of the attack. the assistant commissioner of the metropolitan police, mark rowley, said officers were chasing down suspects. there is plenty more, including eyewitness accounts, on our website. this is bbc news. hello.

after several days of quite cool, showery weather, only subtle changes taking place this weekend. there will be fewer showers around by the time we get to sunday. throughout the weekend, occasional sunshine, it feels quite pleasant. in the showers, it feels quite cold. some quite chilly nights around, as well. perhaps even a touch of frost in a few places. it is chilly because there has been a flow of air from the north. high pressure to the west of us, low pressure to the east. the air coming down from the north, around these pressure systems, and it is unstable air, bringing showers. a few of the showers for western parts of wales, cornwall, devon, a few near these north sea coast zones, in northern scotland, as well. but away from the showery areas, and most of us will be away from the showery areas, we're likely to start the day with some pleasant sunshine. just some areas of cloud and there, but where you've been clear for any period of time overnight,

it will be a chilly start. temperatures are only gradually recovering as we go through the morning. it is still on the breezy side. you'll certainly notice that across northern scotland, and here we're getting a fair few showers coming in on that stiff breeze. so on through the day, then, where you start with some sunshine, the cloud is going to build. there will be the threat of a shower. where you start cloudy, you may well see the sunshine come out for a time, but there is still the threat of a shower. and it could be we see a longer spell of rain moving into parts of western scotland, and into northern ireland. the showers get going elsewhere. there could be some heavy downpours around, especially across some eastern parts of england, that could come with a rumble of thunder, but everywhere at risk of getting at least one shower moving through that may be heavy. temperatures into the mid—teens. as we go on through into the evening, the chance again for a spell of rain, this time affecting parts of wales, south—west england. and even overnight, saturday night into sunday, there could be some heavy rain for some into south—west england. heavy showers close to the south coast, whereas many other places

will become dry, and it is going to be much cooler in rural spots compared with towns and city centres. and some, maybe in scotland, maybe northern ireland as well, we will get close to freezing, for a touch of frost as sunday begins. maybe one or two mist and fog patches, because there are lighter winds on sunday. as high pressure begins to nudge in, looks like it'll give mainly dry weather to scotland, northern ireland, variable cloud. wales and western england will see relatively few showers, but elsewhere across england, a scattering of showers. that could be on the heavy side, but by no means everyone will get one. with lighter winds, more seeing some sunshine. it will feel a little bit warmer by the time we get to sunday. but monday and tuesday is looking pretty quiet, not many showers at all. quite a bit of cloud, a little bit of sunshine. britain's prime minister has raised the country's terror threat assessment to the highest level following a bomb explosion on a rush—hour train in london. theresa may said security analysts had concluded that a further attack might be imminent —

and there would be more armed police on the streets. the united nations security council has strongly condemned north korea for carrying out its latest missile test — calling it ‘highly provocative'. but after an emergency meeting — the un said there would no further sanctions for now. north korea fired a missile over japan for the second time this month. after 20 years in space, the cassini mission to the ringed planet — saturn — has come to a spectacular end. the probe had run out of fuel — and the us space agency — nasa — had commanded it to destroy itself by plunging into the planet's atmosphere. now on bbc news, the week in parliament.