The islands in the East China Sea -- known as the Diaoyu in China and Senkaku in Japan -- are claimed by Beijing but administered by Tokyo and are a frequent hotspot in bilateral tensions.

The Japanese foreign ministry said in a statement released late Saturday that its vice minister lodged "a strong protest" with the Chinese ambassador to Japan "over the intrusion of four China Coast Guard vessels into Japan's territorial waters around the Senkaku Islands" on the same day.

The vice minister also protested "the violation of Japan's territorial airspace by a helicopter launched from one of the China Coast Guard vessels, strongly urging (China) to ensure that similar acts do not recur".

Japan's defence ministry said the helicopter flew within Japanese airspace for about 15 minutes on Saturday near the Senkaku islands.

"The Self-Defence Forces responded by scrambling fighter jets," the ministry said.

Public broadcaster NHK and other local media reported that this is the first time a Chinese government helicopter violated the Japanese airspace off the disputed islands.

On the same day, China's coast guard announced it had used a helicopter to "expel" a Japanese airplane from airspace around the disputed islands.

Liu Dejun, spokesman for China's coast guard, said a Japanese civilian aircraft "illegally entered" the airspace of the islands at 11:19 am (GMT 0219) and left five minutes later.

Beijing frequently announces it has driven Japanese vessels and aircraft away from the islands, but Japanese officials have told AFP that Chinese authorities sometimes announce expulsions when none have occurred.

Unnamed Japanese officials told local media that Beijing was possibly reacting to a small Japanese civilian aircraft flying near the islands.

Chinese and Japanese patrol vessels in the East China Sea have routinely staged dangerous face-offs around disputed islands.

Tensions between China and other claimants to parts of the East and South China Seas has driven Japan to deepen ties with the Philippines and United States.