Two planes flew along the coast between Japan's central and southern regions, passing through the Tsushima Strait and returning the same way, the Joint Staff said in a brief statement.

Japan's Air Self-Defense Force fighter jets "were scrambled in response," it said.

The military also scrambled jets in May against Russian intelligence-gathering planes.

The move comes as Prime Minister Fumio Kishida will meet US President Joe Biden and South Korean leader Yoon Suk Yeol in a summit at the Camp David presidential retreat on Friday.

The leaders will agree to a new three-way crisis hotline and regular military drills and agree to hold trilateral summits each year.

Japan has joined Western allies in sanctioning Moscow over its invasion of Ukraine, and warned of the threat posed by Russia.

Its latest security document, which once called for enhanced ties and cooperation with Russia, now warns that Moscow's joint military drills with China pose a concern.

Last month, the two countries carried out their joint naval exercises in the Sea of Japan and conducted a joint patrol over the Sea of Japan and East China Sea in June.

Japan scrambled jets 778 times in 2022, including 150 against Russia -- the lowest number since 2013 -- according to the Joint Staff.