Japan scrambled fighter jets Thursday to head off a number of Chinese military planes near islands at the centre of a territorial dispute, Japanese media said.

The Chinese planes were spotted on Japanese military radar north of the Japanese-controlled Senkaku islands, known as the Diaoyus in China, the Fuji TV network reported, quoting Japanese government officials.

They did not violate territorial airspace over the islands but flew inside Japan's so-called air defence identification zone, the report said.

The Japanese defence ministry press office did not confirm the report.

The Chinese planes were gone when F-15 jet fighters from an airbase on Japan's main Okinawan island reached the area, the report said, adding the Chinese flights continued until about 5:00 pm (0800 GMT).

Chinese government ships and planes have been seen off the disputed islands numerous times since Japan nationalised them in September, sometimes within the 12 nautical-mile territorial zone.

The coastguard said Thursday evening they were not aware of any Chinese military aircraft in the area.

On Wednesday the conservative Sankei Shimbun reported that the number of Chinese military planes nearing Japanese territory had increased since Japan nationalised the islands.

The paper said Japan's air force had scrambled fighter jets to intercept Chinese military aircraft numerous times over the past few months. Defence officials said they could not confirm the report.

F-15s were sent airborne to head off Chinese state-owned -- but not military -- planes four times in December, including an occasion when Japanese airspace was breached, the defence ministry has said.

They were also mobilised once last week, it said.

Japan is Friday expected to approve a huge stimulus package aimed at breathing life into its flagging economy.

Around 180 billion yen ($2.1 billion) of the total 20 trillion yen set to be announced is expected to be allocated to military spending.

A defence ministry spokesman told AFP the cash would be used to buy missiles, helicopters and to refurbish fighter jets to cope with the changing security environment in the region.