Two Russian strategic bomber planes flew over the Sea of Japan for more than seven hours, the Russian defence ministry said on Tuesday in a statement released as Japan's prime minister was beginning a visit to Ukraine.
The Tupolev Tu-95MS planes are capable of carrying nuclear weapons and Moscow regularly flies them over international waters in the Arctic, North Atlantic and Pacific as a show of strength.
The timing of the latest flight appeared 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.
Japanese national broadcaster NHK showed Prime Ministers Kishida boarding a train at the Polish town of Przemysl near the Ukraine border.
Russia said the strategic bombers made a "planned flight", escorted by fighter planes. It was carried out in strict compliance with international law and was made over neutral waters, the defence ministry said.
In February, North American air defence forces were sent to intercept several Russian strategic bombers and fighter jets as they flew over international airspace near Alaska.
Japan, which has its own territorial dispute with Moscow over islands in the north Pacific that dates back to the end of World War Two, is a key Asian ally of the United States and a member of the Group of Seven rich democracies, and has joined Western sanctions against Russia.
Fumio Kishida's trip to Ukraine also coincides with Chinese President Xi Jinping's state visit to Moscow.
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