the issue was revived in april when the outspoken governor of tokyo ishihara proposed to purchase the island from their private owners. yoke heeko noda said the central government is considering similar plans. >> translator: the point is for japan to administer the islands in a peaceful and stable manner. we're communicate with the private owners and working on a comprehensive plan. >> the proposal drew furious comments on chinese online forums. >> translator: the chinese military should occupy the islands. >> translator: japan needs to pay for its attitude. >> monday's press briefing at the foreign ministry suggested chinese officials were ready for stronger action. >> translator: buying or selling china's sacred land is unacceptable. the government will do what it takes to protect her sovereignty over the islands. >> two days later, three chinese patrol boats entered waters near the islands and were challenged by japan coast guard vessels. the confrontation lasted several hours. >> translator: this was a significant case of trespassing into our territorial waters. we'll have to keep

ishihara says he can't understand why. >> translator: japanese nationals need to stay on the islands. self-defense force personnel should be deployed there. japan needs to permanently station japanese people in its territory. >> government leaders have also announced plans to buy the islands. they say they are studying ways to use the land. >>> in other news, japan is planning to start the first trial production of shale oil this autumn. the oil is contained in a sedimentary rock called shale found in bedrocks deep underground. its excavation had been considered difficult for a long time. but the development of new technologies has made shale oil drilling easier, and surging fuel prices have made this new source of energy more attractive. the united states has been trying to tap shale oil for some time, and now japan petroleum exploration company or japex plans to go ahead with the first test production in the country. the test is scheduled 1,800 meters underground at the ayukawa oil-gas field in southern akita prefecture. japex also plans tests at two other oil-gas fields also in aki