The Chinese aircraft was "confirmed to have violated the territorial airspace off the Danjo Islands in Nagasaki Prefecture," the ministry said in a statement, adding it had launched "fighter jets on an emergency basis".

China's "Y-9 intelligence-gathering" aircraft entered Japanese airspace at 11:29 am (0229 GMT) for around two minutes, the ministry added.

There was no comment from Chinese authorities.

Local media including public broadcaster NHK said the incident marked the first incursion by the Chinese military's aircraft into Japan's airspace.

The ministry said steps were taken by the SDF such as "issuing warnings" to the aircraft, but NHK reported that no weapons, such as flare guns, were used as an alert.

In response to the incident, vice foreign minister Masataka Okano summoned China's acting ambassador to Japan late Monday, and "lodged firm protest" with the official, as well as calling for measures against a recurrence, the foreign ministry said in a statement.

The Chinese diplomat said in response that the matter would be reported to Beijing, according to the ministry.

Japanese and Chinese vessels have previously been involved in tense incidents in disputed areas, in particular the Senkaku islands in the East China Sea, known by Beijing as the Diaoyus.

The remote chain of islands have fuelled diplomatic tensions and been the scene of confrontations between Japanese coastguard vessels and Chinese fishing boats.

Beijing has grown more assertive about its claim to the islands in recent years, with Tokyo reporting the presence of Chinese coast guard vessels, a naval ship and even a nuclear-powered submarine.

In the past, two non-military aircraft from China -- a propeller plane and a small drone -- were confirmed to have forayed into the Japanese airspace near the Senkaku islands in 2012 and 2017, according to NHK.

Beijing claims the South China Sea -- through which trillions of dollars of trade passes annually -- almost in its entirety despite an international court ruling that its assertion has no legal basis.

The Danjo Islands are a group of small islets located in the East China Sea, off Japan's southern Nagasaki region.

Japan in recent years has strengthened security ties with the United States to counter China's growing assertiveness in the region, boosting defence spending and moving to acquire "counter-strike" capabilities.

At the same time it has boosted military ties with the Philippines, which has also been involved in recent territorial standoffs, as well as South Korea.