US and Japanese fighter jets on Tuesday carried out joint air exercises, an official said, days after Chinese and Japanese military planes shadowed each other near disputed islands in the East China Sea.
The five-day exercise involves six US FA-18 fighters and around 90 American personnel, along with four Japanese F-4 jets and an unspecified number of people, the official said.
The drill is being carried out over Pacific waters off the coast of Shikoku, the fourth largest of Japan's islands.
It comes weeks after hawkish new Prime Minister Shinzo Abe won an election landslide following campaign promises to re-invigorate Tokyo's security alliance with Washington and take a more robust line against Beijing.
The exercise also comes as a stand-off between China and Japan over the sovereignty of the disputed East China Sea islands shows no signs of letting up.
Tokyo reportedly scrambled fighter jets on Thursday to head off Chinese military planes in an area adjoining the airspace of the Japanese-controlled Senkaku islands, which Beijing claims as the Diaoyus.
A Chinese defence ministry official later said two J-10 fighters flew to the area to monitor two Japanese F-15 fighters that had trailed a Chinese Y-8 aircraft, according to China's official Xinhua news agency.
On Tuesday, one Chinese state-owned Y-12 plane flew close to -- but not inside -- the airspace of the disputed islands, triggering the scrambling of Japanese fighter jets, the defence ministry in Tokyo said.
The row between Asia's two largest economies over the uninhabited, but potentially resource-rich islands blistered in September when Tokyo nationalised three of them.
Chinese government ships have repeatedly gone to the archipelago's territorial waters since then.
Beijing insists it is simply patrolling islands it has owned since ancient times. Commentators say China wants to prove that Japan does not have effective control over the chain and draw Tokyo into concessions.
On Sunday, Japan's Ground Self-Defense Force carried out the nation's first military exercise designed to recapture "a remote island invaded by an enemy force".
Some 300 troops took part in the 40-minute drill with 20 warplanes and more than 30 military vehicles at the Narashino Garrison in Chiba, southeast of Tokyo.
Some 80 personnel from the SDF's First Airborne Brigade rappelled from helicopters to demonstrate manoeuvres to counter an enemy invasion of a remote island.
In October Japan and the US dropped plans for a joint drill to simulate the retaking of a remote island, reportedly because Tokyo did not wish to provoke Beijing further.
There was no outward indication that the joint Japan-US exercise that began Monday and runs until Friday was aimed at China, and the area being used was a long way from any contentious zone.
The official told AFP the drill had previously been staged from Iwakuni in the far west of Honshu, but had been moved to Miyazaki in the south of Kyushu out of consideration for people living near the base.
While the security alliance receives wide public support in Japan, there are tensions between bases and their host communities, particularly over noise and the risk of accidents, as well as associated crime.
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