Japan on Tuesday lambasted what it said was a violation of its airspace by a Chinese military plane, describing it as "utterly unacceptable."

Japan's chief government spokesman, Yoshimasa Hayashi, told reporters Monday's incursion "threatens Japan's security."

What do we know about the Chinese aircraft?

Tokyo said it scrambled fighter jets after a Chinese Y-9 surveillance aircraft entered its airspace for two minutes, flying over the Danjo Islands in Nagasaki Prefecture.

"We understand that this is the first confirmed and announced airspace incursion by a Chinese military aircraft since we started the anti-airspace incursion measures," Hayashi told a regular briefing.

He added that the government continues to monitor increasing Chinese military activity near Japan, adding it will be fully prepared for any airspace violation.

Tokyo summons Chinese diplomat

Tokyo summoned a Chinese embassy official in protest. Hayashi declined to comment on the details of the diplomatic talks.

"We refrain from giving a definite answer as to the intended purpose of the Chinese aircraft's action. However, recent [Chinese] military activities near Japan have a tendency to expand and become increasingly active," he said.

A China State Oceanic Administration plane violated Japan's airspace in 2012 while in 2017, a China Coast Guard drone also breached Japan's airspace, according to Japan's public broadcaster NHK.

rmt/jsi (AFP, Reuters)