Sources have told NHK that a Chinese military aircraft which intruded into Japan's southwestern airspace on Monday circled nearby waters several times beforehand.

Japan's Defense Ministry said on Monday that the Chinese military's Y-9 intelligence-gathering aircraft flew in Japan's territorial airspace over waters off the Danjo Islands in Goto City, Nagasaki Prefecture.

It was the first time that a violation of Japan's territorial airspace by a Chinese military plane was confirmed.

The ministry said the aircraft came from the direction of mainland China, flew toward Kyushu, and intruded into Japan's airspace after circling over waters southeast of the Danjo Islands.

Sources told NHK that the aircraft had circled the area several times before the intrusion.

The sources said Air Self-Defense Force fighters radioed the Chinese aircraft not to get close to Japanese airspace, while the aircraft was circling. But it flew inside Japanese airspace for about two minutes, and then circled over nearby waters for more than 90 minutes.

The Defense Ministry is trying to determine the purpose of the aircraft's maneuvers.