Three Chinese coastguard vessels spent more than two hours in the 12-nautical-mile territorial waters off one of the Senkakus, which China claims and calls the Diaoyus, Japan's coastguard said.

They left the waters at about 12:30 pm (0330 GMT), it said.

China's State Oceanic Administration said three of its coastguard ships were patrolling "territorial waters surrounding the Diaoyu islands" on Sunday, according to official state news agency Xinhua.

It came days after a diplomatic battle over Japanese Prime Minister Shinzo Abe's visit to a contested war shrine reached the UN Security Council, with China and Japan accusing each other of threatening stability.

China's UN ambassador, Liu Jieyi, seized upon a debate on the lessons of conflict to slam Abe for going to the Yasukuni Shrine, which honours war criminals among the country's war dead.

Last week also saw a report in Japan's Asahi Shimbun newspaper that Chinese air force officials had drafted proposals for a new Air Defence Identification Zone (ADIZ) over the South China Sea.

The United States has warned China that any move to declare a new air zone including disputed islands would be seen "as a provocative and unilateral act that would raise tensions and call into serious question China's commitment to diplomatically manage territorial disputes," State Department deputy spokeswoman Marie Harf told reporters.

She stressed, however, that the reports were "unconfirmed" at this time.

China's foreign ministry spokesman Hong Lei said right-wing forces in Japan had repeatedly made such allegations with the intention of shifting international attention from the "plot" to change Japan's pacifist constitution, Xinhua reported.

"We sternly warned these forces not to mislead public opinions with rumours and play up tensions for their own selfish benefit," he said in a press release Saturday quoted by Xinhua.

Hong said China had the right to adopt all measures, including setting up air defence zones, to safeguard national security, according to Xinhua.

Beijing claims the South China Sea almost in its entirety, even areas far from its shoreline.

In November China abruptly declared an ADIZ over the East China Sea, including the disputed islands at the heart of the sovereignty row with Tokyo, sparking international criticism.

Chinese state-owned ships and aircraft have regularly approached the Senkakus to demonstrate Beijing's territorial claims, particularly after Japan nationalised some of the islands in September 2012.