Flexing its muscles, China for the first time sent a marine surveillance plane to join its warships to monitor the disputed islands with Japan, forcing Tokyo to scramble eight F-15 fighter jets.
The jets were mobilised after a Chinese maritime aircraft ventured over the Senkaku islands, which China calls the Diaoyus, just after 11 am (0200 GMT), Chief Cabinet Secretary Osamu Fujimura told reporters in Tokyo.
"It was a fixed-wing Y-12 aeroplane belonging to the Chinese State Oceanic Administration. We confirmed that this aeroplane flew in our country's airspace," he said.
China's move to sent the plane came after it regularised patrols by its maritime and naval vessels, challenging Tokyo's hold over the unmanned islets.
The plane, B-3837 conducted joint patrols with a fleet of four surveillance ships, state-run Xinhua news agency quoted a statement by the state oceanic administration. The fleet declared the Chinese government's stance and ordered the Japanese ships that had entered China's territorial waters to leave the area immediately, the statement said.
Japan mobilised eight F-15 jets and an E2C early-warning aircraft, the Asahi Shimbun reported, citing a defence ministry source. But the incident appeared to have passed off without any direct confrontation.
This is the first time China has deployed maritime planes after it began sending the patrol ships since September this year questioning Japan's move to buy the islands.
Before that China has not seriously challenged Japan's administrative hold on the islands, though it all along claimed sovereignty over them. China termed Japan's move provocative and said it would continue to make its presence felt around the islands.
Analysts say that the two countries could make an attempt to break the impasse after the current elections in Japan. In Beijing, China's foreign ministry said the flight had been routine.
"China's maritime surveillance plane flying over the Diaoyu islands is completely normal," said spokesman Hong Lei.