Chinese patrol boats confronted Japanese vessels near a disputed East China Sea archipelago early Tuesday, the latest in a series of such encounters following Tokyo's nationalization of the islands last month.

Four ships from China Marine Surveillance entered waters near the islands at 10 a.m. (0200 GMT), according to a statement from the State Oceanic Administration that commands the service. The ships conducted surveillance on the on Japanese Coast Guard vessels in the area, "sternly expressed" China's sovereignty claim over the islands and "carried out expulsion measures," the administration said.

Japanese Coast Guard spokesman Yuji Kito said ships from both countries flashed signs saying they were in their own territorial waters and demanding the other side leave.

"The Chinese flashed the signs in Chinese and Japanese," said Kito, speaking by phone from Coast Guard headquarters in Okinawa, which has jurisdiction over the islands. "They have done this before and so have we." He said the situation was not more intense than previous encounters.

The uninhabited islets, known as Senkaku in Japan and Diaoyu in China, are also claimed by Taiwan.

China has launched increasingly frequent patrols around the islands since angrily protesting the Japanese government's decision to purchase them from their private owners. Chinese ships have at times entered the 22-kilometer (12-nautical mile) zone that Tokyo considers its territorial waters near the islands and Chinese aircraft have also stepped up activity around them.

Tokyo's nationalization sparked violent protests in dozens of Chinese cities and sent relations nose diving, with trade ties among the worst to suffer.

China has demanded Tokyo acknowledge the sovereignty dispute, and the sides have held low-key talks aimed at reducing tensions.

Japan needs to "face up to the current reality, recognize the controversy, correct their mistakes and negotiate," Chinese Foreign Ministry spokesman Hong Lei told a regularly scheduled news conference Tuesday. "We hope Japan can show real sincerity and action to make efforts in solving the current issue."


Associated Press writer Eric Talmadge in Tokyo contributed to this report.