The number of emergency take-offs by Air Self-Defense Force jets against Chinese aircraft sharply increased over the July-September period, as the Japanese government moved forward with the purchase of the Senkaku Islands.

Officials at the Defense Ministry say the ASDF scrambled its planes 69 times to intercept Chinese aircraft approaching Japanese airspace between April and September.

The number of scrambling incidents between April and June was 15. But the figure for the next 3 months more than tripled to 54 as relations between Japan and China soured over the issue of the Senkaku Islands.

The ministry officials say many Chinese airplanes entered Japan's air defense identification zone from the north or the west and turned back at about 200 kilometers from the Senkaku Islands. They also say many of the aircraft were patrol or surveillance planes.

The Japanese government purchased 3 of the islands from a private Japanese owner in September. The islands in the East China Sea are also claimed by China and Taiwan.

Chief of Staff of the Self-Defense Forces, Shigeru Iwasaki told reporters on Thursday that Chinese warplanes, as well as navy fleets, have been stepping up operations in the East China Sea over the past few years.

Iwasaki said it will be important for Japan's warning and surveillance activities to investigate their recent activities and analyze them from many angles.