BEIJING (Reuters) - China’s air force chief defended military maneuvers in the Sea of Japan, saying the waters did not belong to Tokyo, after a Japanese defense review warned of increasing Chinese military activity there.

Japan worries that China’s probing of its air defenses 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 1,400 km (870 miles) south toward Taiwan.

In an annual defense white paper released on Tuesday, Japan said the number of its jet scrambles against Chinese aircraft hit a record in the year to March 2017.

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 northeastern city of Changchun.

“We must carry out drills at sea. China’s air force cannot simply guard on land and not go out,” Ma said in a report broadcast by Hong Kong-based Phoenix Television, which was posted to the air force’s official microblog late 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 separates Japan from the Korean peninsula. China said in July 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.

Increasing activity by China’s rapidly modernizing military has boosted tension in East Asia since the start of the year, as North Korea persists with ballistic missile and nuclear bomb tests that have stoked fears in Japan, the United States and elsewhere.