Tokyo has lodged a protest with Moscow after a foreign aircraft -- believed to be Russian -- briefly violated its airspace, prompting Tokyo to scramble four fighter jets, government officials said Wednesday.
The foreign ministry made the protest shortly after the plane entered Japanese airspace off the coast of the northernmost main island of Hokkaido, near a disputed island chain, on Tuesday afternoon.
"We made the protest through the Russian embassy in Tokyo," a foreign ministry official told AFP.
"The Russian side did not confirm the case, only saying they will check."
The Japanese Air Self-Defense Force scrambled four jets to head off the intruder, which it believed was Russian after analysing its course, a defence ministry official said.
If confirmed, this would be the first time Russian planes have entered Japanese airspace since August 2013, when two Tu-95 Russian strategic bombers were intercepted off the southwestern Okinoshima Island, the ministry said.
Sixteen seconds after entering Japanese airspace, the plane left toward the Kuril island chain, claimed by Tokyo but controlled by Russia, the ministry added.