The Japanese Air Self-Defense Force scrambled four jets to head off the intruder on Tuesday. (Representational Image)
Japan scrambled four fighter jets to intercept a foreign aircraft -- believed to have been Russian -- which briefly violated its airspace, the defence ministry was reported as saying today.
The plane entered Japanese airspace off the coast of the northernmost main island of Hokkaido, the Kyodo and Jiji news agencies said.
The Japanese Air Self-Defense Force scrambled four jets to head off the intruder on Tuesday, Jiji added.
The defence ministry said it believed the plane was Russian after analysing its vapour trail, according to Jiji, adding officials said the aircraft left Japanese airspace quickly.
The plane was in Japanese airspace for about 16 seconds.
If Russian planes were found to have been involved, it would be the first such incident for two years.
Russian military jets have not entered Japanese airspace for more than two years, the defence ministry was quoted as saying, when two Tu-95 Russian strategic bombers were intercepted off Okinoshima Island in south west Japan, Kyodo quoted the defence ministry as saying.
Japan's foreign ministry has lodged a protest with Russia, Jiji said.