BEIJING • China's air force chief defended military manoeuvres in the Sea of Japan - also known as the East Sea - saying the waters did not belong to Tokyo, after a Japanese defence review warned of increasing Chinese military activity there.

Japan worries that China's probing of its air defences is part of a push to extend its military influence in the East China Sea and western Pacific, where Japan controls an island chain stretching 1,400km south towards Taiwan.

In an annual Defence White Paper released on Tuesday, Japan said the number of its jet scrambles against Chinese aircraft hit a record high in the year till March.

It warned that Chinese naval and air force activities in the Sea of Japan could pick up pace.

"The Sea of Japan is not Japan's sea," People's Liberation Army Air Force commander Ma Xiaotian said on Thursday, in response to a question at a military event in the north-eastern city of Changchun.

"We must carry out drills at sea. China's air force cannot simply guard on land and not go out," he said in a report broadcast by Hong Kong-based Phoenix Television, which was posted to the air force's official microblog late on the same day.

"But (activities) in the Sea of Japan are still not that many. What they have said is a bit of an exaggeration."

Tokyo's ties with Beijing have long been plagued by a territorial dispute over a group of tiny, uninhabited East China Sea islets and the legacy of Japan's wartime aggression.

The Sea of Japan, or East Sea, separates Japan from the Korean peninsula.

China said last month that its navy had the right to pass though a strait linking it with the Pacific Ocean, after one of its warships entered the area.

Meanwhile, Beijing voiced displeasure yesterday after a United States warship sailed near an artificial island in the disputed South China Sea, an operation that prompted the Chinese navy to warn off the American destroyer.

The USS John S. McCain destroyer sailed within six nautical miles of Mischief Reef - an artificial island built by China - on Thursday as part of a "freedom of navigation" operation, a US official said.

REUTERS, AGENCE FRANCE-PRESSE