The Russian defence ministry said on Tuesday that two Russian strategic bomber planes flew over the Sea of Japan for more than seven hours, as Japan's prime minister was beginning a visit to Ukraine.
The Tupolev Tu 95 MS planes are capable of carrying nuclear weapons and Moscow regularly flies them over international waters in the North Atlantic, the Arctic, and the Pacific as a show of strength.
The timing of the latest flight appeared to be more pointed than usual, as Japanese Prime Minister Fumio Kishida was due in Kyiv later on a visit to show solidarity with Ukrainian President Volodymyr Zelenskiy in the war against Russia.
The Japanese national broadcaster NHK showed Kishida boarding a train at the Polish town of Przemysl near the Ukraine border.
Russia said that strategic bombers made a planned flight escorted by fighter planes. The defence ministry said it was carried out in strict compliance with international law and made over neutral waters.