Russia's Defence Ministry said on Tuesday two Russian strategic bombers - capable of carrying nuclear warheads - carried out routine patrol flights over the Sea of Okhotsk and the Bering Sea, off Russia's Far East, TASS news agency reported.
Japan's Defence Ministry later said in a statement that it had scrambled a jet fighter in response to Russian information-gathering aircraft over the Sea of Japan.
Japan's Chief Cabinet Secretary Hirokazu Matsuno said on Monday that Tokyo had lodged a protest with Russia over its military exercises around disputed islands near Japan's Hokkaido.