This is the dramatic moment a Russian fighter jet intercepted a pair of US nuclear bombers over the Baltic Sea, just days after an American drone was downed.

Russia's defense ministry said a single Su-35 was scrambled to meet the B-52 strategic bombers that were flying towards the Russian border on Monday, but that it returned to base after they moved away following a tense standoff.

The development came as Moscow said it had flown two of its nuclear bombers over the Sea of Japan for more than seven hours, in a statement released as Japan's prime minister was beginning a surprise visit to Ukraine - and as China's premier Xi Jinping continues his visit to Moscow.

Russia's 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 and as an intimidation tactic.

It also followed the March 14 crash of a US military surveillance drone into the Black Sea after it was intercepted by Russian jets, in the first known direct military encounter between Russia and the US since Russia invaded Ukraine.