Japanese fighter jets have been scrambled 30 times to turn away Chinese planes approaching Japan's airspace in the last six months, more than twice the 13 times in the same period last year, officials said Wednesday.

The increased defensive posture reflects the growing tensions between Japan and China, which are squabbling over interpretations of their wartime past, undersea gas deposits, and ownership of East China Sea islands.

An Air Self Defense Force spokesman said Japan's fighter jets had scrambled 30 times in response to what were believed to be Chinese military planes in the six months from April to September. Japan's fiscal year starts in April.

The spokesman, who spoke on condition of anonymity in line with agency policy, added that fighter jets also have been deployed since October, but declined to say how many times.

That would surpass the record-high 30 scramblings in response to Chinese planes in all of 1998. Japan began keeping track of the number of fighter jet mobilizations against specified countries in 1995.

Another official of the Air Self Defense Force declined to comment on the types of Chinese planes or what they were doing. He said there have been no major confrontations between Japanese fighter jets and foreign military planes in 2005.

The newspaper Sankei Shimbun said Wednesday that Chinese surveillance planes were flying over natural gas sites in the East China Sea that are claimed by both Tokyo and Beijing.

Another 72 scramblings were triggered by Russian planes during the April-September period this year, according to the first official. He did not provide any other details. Japan and Russia both claim islands off Japan's northern main island of Hokkaido that were seized by Moscow near the end of World War II.