BEIJING - Six Chinese ships sailed into the territorial waters of islands claimed by both China and Japan yesterday morning, as tensions between the East Asian powers showed no sign of easing.
The maritime surveillance ships reached the waters around the islands, called Diaoyu by the Chinese but controlled and called Senkaku by the Japanese, to carry out patrols and law enforcement, said China's Xinhua news agency.
The ships left by early afternoon, but not before exchanging words with the Japanese.
Xinhua reported that when a Japanese Coast Guard ship demanded that China's Haijian 50 leave its waters, a crew member on the Chinese ship retorted in Japanese: "This is China's territorial waters. Please leave immediately."
China has also sought to shore up its claims using legal means. On Thursday, envoy Li Baodong filed the baselines and coordinates of its territorial waters around the islands with the United Nations, in accordance with the UN Convention on the Law of the Sea.
China's actions come after Japan bought the islands from a private Japanese owner on Tuesday to bring them under state control - decried by China as illegal.
But Japan does not seem to be backing down. Yesterday, it summoned the Chinese ambassador in protest against the Chinese ships' "incursion" into its territorial waters, while Prime Minister Yoshihiko Noda promised "all possible measures" to secure the islands.
While armed hostilities remain a long way off, analysts said the possibility cannot be ruled out, especially in a period of political transition in both countries.
Beijing is poised for a change of top leaders by the year end, while Tokyo may hold Lower House polls as early as November. This makes them vulnerable to public pressure for a strong stance over territorial disputes, said analysts.
Annexed by Japan in 1895, the five islets and three barren rocks in question came under the control of the United States after World War II. When Okinawa was returned to Japan in 1972, the islands near Okinawa were also put under Japan's administration.
The Americans, meanwhile, have called for calm. US Defence Secretary Leon Panetta is visiting Japan and China next week, in part to discuss the spat.
The stand-off marks a new low in ties between China and Japan since 1978, when they agreed to shelve differences over the islands, noted some analysts. This consensus was part of the foundation for their friendly ties, said researcher Tetsuo Kotani of the Japan Institute of International Affairs.
"Now that it is gone, bilateral political, economic and cultural relations are facing a difficult time," he told The Straits Times.
Ties have been hit on all fronts, be it the cancelling of official visits or the harassment of Japanese in Shanghai, the latter prompting Tokyo to issue a safety warning to its citizens in China. From leaders to ordinary citizens, China has kept pressure on Japan.
"The women of China resolutely oppose Japan's so-called islands purchase and will not tolerate any country violating China's sacred territorial grounds," the All-China Women's Federation said in a statement.