TOKYO - China has asked Japan to clarify reports that Japan's Air Self-Defence Force (ASDF) is preparing a manual to deal with increasing incursions into Japanese airspace by foreign planes, especially Chinese fighter jets.

Noting that the Diaoyu islands - Senkaku to the Japanese - are Chinese sovereign territory, foreign ministry spokesman Hong Lei told China News Service: "China will react if Japan heightens the issue, and Japan must face all the consequences."

The Sankei Shimbun daily had said on Wednesday the manual is being drawn up to deal with the growing incidence of Chinese fighter jets and intelligence gathering planes either coming close to, or entering, Japanese airspace, particularly over the disputed Senkaku islands.

The ASDF was prompted to compile a manual last month after a plane belonging to the Chinese national maritime authority intruded into Japanese airspace over the Senkakus.

The Senkakus are under Japan's administrative control but are also claimed by China.

The manual will have detailed procedures for Japanese fighter jets to follow when they have to escort errant foreign aircraft to make a forced landing at a Japanese airport. The ASDF has not made such enforced landings before.

This month, the Defence Ministry said ASDF planes were scrambled 563 times from April to September last year, 51 per cent of the time in response to violations or near-violations of Japanese airspace by Chinese aircraft.