Two China Marine Surveillance ships reached waters around the Diaoyu Islands in the East China Sea yesterday morning to assert the country's sovereignty in a show of protest against Japan's "purchase" of the largely barren outcroppings from so-called private Japanese owners.
The CMS said it had drafted an action plan to safeguard sovereignty and would take action pending development of the situation.
The marine agency is a paramilitary force whose ships are often lightly armed.
Japan's coast guard said it had not taken any special measures in response to the Chinese patrol boats although it was continuing to monitor the situation.
Japan's central government announced a deal this week with the Japanese family it recognizes as the owner of the islands. Chief Cabinet Secretary Osamu Fujimura told reporters the government budgeted 2.05 billion yen (US$26 million) for the purchase. The government and the family signed a deal yesterday, a move threatening to deepen strains between Asia's two biggest economies.
The Chinese military's top newspaper accused Japan of "playing with fire," and the Defense Ministry warned that more steps could follow. "The Chinese military expresses its staunch opposition and strong protest over this," Defense Ministry spokesman Geng Yansheng said yesterday.
"The Chinese government and military are unwavering in their determination and will defend national territorial sovereignty. We are closely following developments, and reserve the power to adopt corresponding measures," Geng said.
He accused Japan of "using all kinds of excuses to expand its armaments, and repeatedly creating regional tensions."
In a statement read out on a state television news broadcast, the foreign affairs committee of China's legislature said yesterday: "We strongly urge Japan to fully grasp the dangerousness of the present situation and step back from the edge of a precipice over the Diaoyu Islands issue."
Japanese Prime Minister Yoshihiko Noda, in an address to senior military officers, made no direct reference to the issue, but pointed to China's growing military clout as one of challenges Japan had to contend with.
The Japanese foreign ministry said it was sending its Asia department chief to Beijing for talks to "avoid misunderstanding and lack of explanation on the issue."
China has announced coordinates marking out waters off the Diaoyu Islands, apparently for the first time after doing so earlier for the mainland and other islands. The move is another step, along with announcements of an intention to use law enforcement vessels, to defend its sovereignty over the islands.