TOKYO (AFP) - Japan scrambled fighter jets on Monday after an unidentified drone flew near Tokyo-controlled islands at the centre of a bitter dispute with China, a defence ministry spokesman said.

It was the first reported incident of its kind.

Japan's Air Self-Defence Force sent an unspecified number of jets to the area, the official said.

The drones did not enter Japanese airspace, the official said.

A second Japanese defence ministry official said the nationality of the drone was not clear, but added that it came from the north-west and and was last seen flying back in that direction.

China does have drones but when asked about the incident, foreign ministry spokesman Hong Lei said: "I am not aware of the situation."

On Sunday, Japan scrambled fighter jets against two Chinese bombers that flew from the East China Sea into the Pacific, through a gap between islands in the Okinawa chain, the defence ministry said.

And two weeks ago, fighters were dispatched to head off a Chinese government plane flying towards the Senkaku islands, which Beijing calls the Diaoyus and claims as its own.

A Y-12 propeller plane flew about 100 kilometres from airspace around the islands on August 26, before heading back towards China after Japan's military planes became airborne.

In December, a similar plane from China's State Oceanic Administration breached airspace over the disputed islands, prompting the launch of Japanese F-15s.

It was the first known incursion by a Chinese plane into Japanese airspace, the government said at the time.

Friday's reports came as four Chinese coastguard ships sailed in the so-called contiguous zone that surrounds territorial waters around the islands.

It was the latest in a series of such sorties by Chinese government ships since Tokyo nationalised three islands in the chain last September, reigniting a long-simmering dispute.