Japan scrambled fighter jets Monday after a Russian surveillance plane entered Japanese airspace three times, the Defense Ministry said, with Air Self-Defense Force fighters deploying flares for the first time since Tokyo began enforcing measures against such incursions.

Defense Minister Minoru Kihara said a Russian IL-38 patrol aircraft had violated Japanese airspace off Hokkaido’s Rebun Island three times, for periods of 1 minute, 30 seconds and 1 minute, on Monday afternoon.

“This violation of our airspace is extremely regrettable, and today we have lodged a stern protest with the Russian government via diplomatic channels, while also strongly requesting that they prevent a recurrence,” Kihara told a hastily organized news conference at the ministry.

The airspace incursion was the first publicly announced entry into Japanese airspace by a Russian military aircraft since 2019, Kihara said, and followed an incursion by a Chinese military spy plane off Nagasaki Prefecture late last month. Japan called that move “utterly unacceptable” and said it considered the flight a threat to the country’s safety.

In responding to Monday's incidents, Kihara said ASDF F-15 and F-35 fighter jets had issued warnings over the radio, deploying the flares — which he said was “one measure we can take in the event of a violation of our airspace” — on the Russian aircraft’s third incursion.

Flares are intended to be fired to confuse heat-seeking missiles, but are also commonly deployed to warn away other aircraft. Kihara did not offer any further details about the encounters, but said the Russian aircraft had not made any threatening moves toward the ASDF fighters.

The defense chief, however, said it was possible the incursions were related to joint Russian military exercises with China in the area.