john hendry has more. >> reporter: the air strikes are effective in blocking troops from moving from one area to another. they can keep troops contained essentially, which is what those air strikes are trying to do around the area of mosul here in northern iraq, trying to cut the islamic state off from their supply lines in syria. but what air strikes cannot do is fight the kind of urban battle you have in tikrit. we have seen leaflets warning people to leave, that is likely before air strikes and a possible larger ground strike, but you cannot do that strictly with air strikes. and on the car bomb i referenced, it sounds like a truck filled with explosives exploded at the gate of camp spiker, north of tikrit, just the latest example of -- of a very bloody war going on here. >> meanwhile fighters from the islamic state group in northern iraq have kidnapped at least 50 men. those abductions happened in a city village southwest of kurkurk. the i.s. fighters fought with armed tribesmen in the same village on tuesday. >> al-qaeda leader has announced plans to expand the group's network i