Tokyo lodged a protest with Moscow over what Japan suspects was a Russian chopper violating its airspace off the country’s northernmost island of Hokkaido, Kyodo reported.

The Japanese Defense Ministry earlier said that a suspected Russian helicopter entered Japan’s airspace over the Nemuro Peninsula at about 12:44 p.m. local time (3:44 a.m. GMT).

Japan’s Air Self-Defense Force scrambled fighter jets to warn away the aircraft. Also, Kyodo said, Tokyo demanded that Moscow take measures to prevent such incidents from happening.