BEIJING (REUTERS) - China's Defence Ministry complained on Friday that Japanese surveillance activities threatened the safety of Chinese ships and aircraft, raising the issue after Japan said earlier this week that its jet fighter scrambles had hit levels unseen since the Cold War.

Japan's air force said the increased number of scrambles were in response to Russian bombers probing its northern skies and Chinese combat aircraft intruding into its southern air space.

China's Defence Ministry, in a statement faxed to Reuters, said that Chinese air force activities accorded with both international law and norms.

"In recent years, Japanese ships and aircraft have often followed and monitored for lengthy periods and at close distances Chinese ships and aircraft, threatening the safety of the Chinese side," it said.

"This is the cause of the safety issue in the seas and air between China and Japan," the ministry added.

"China has a grip on the tracking and surveillance by Japanese ships and aircraft, and takes necessary steps to deal with it," it said, without elaborating.

Japan says the Chinese fighter incursions are concentrated in the East China Sea, close to uninhabited islets claimed by Japan and China.

Coastguard ships and fighter aircraft from both sides routinely face off around the islands, fuelling fears that an accident could spark a clash.