Japanese fighter jets fired warnings flares against a Russian military aircraft that Tokyo said repeatedly entered the country’s territorial airspace, in an unprecedented move against a foreign plane.

The infringements were the first by Russia in five years, according to the Japanese defense ministry. A fighter fired a warning flare in response.

Japan scrambled fighter jets and used flares to warn off a Russian military plane that breached Japanese airspace on Sept. 23, Japanese Defense Minister Minoru Kihara said. The airspace violation could be related to the joint military exercises Russia and China planned to participate in during September.