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's defense minister said the use of flares was a legitimate response to airspace violation and "we plan to use it without hesitation."

Russia and Japan have a territorial dispute over Russian-held islands near Hokkaido that were seized from Japan in the final days of World War II. Russian aircraft occasionally enter Japanese airspace, prompting Japan to scramble fighter jets in response.