WASHINGTON -- The U.S. and Russia accused each other of unsafe actions on Friday after an American guided-missile cruiser and a Russian destroyer came within 50 metres of each other in the East China Sea.

The U.S. 7th Fleet said the Russian destroyer put the safety of the USS Chancellorsville and its crew at risk, forcing it to reverse all engines at full throttle to avoid a collision.

It said a helicopter that was operating at sea was preparing to land on the Chancellorsville, which was travelling on a steady course, when the Russian destroyer, travelling behind the U.S. ship, speeded up and approached as close as 15-30 metres.

Clay Doss, spokesman for the Japan-based 7th Fleet, said no one was injured and he was not aware of any damage to the ship.

"We consider Russia's actions during this interaction as unsafe and unprofessional and not in accordance with the International Regulations for Preventing Collisions at Sea (COLREGS), 'Rules of the Road,' and internationally recognized maritime customs," the 7th Fleet said in a statement.

It was the first such incident involving warships in the region since September, when a Chinese ship manoeuvred close to an American destroyer in the South China Sea, an incident the U.S. also labeled unprofessional and unsafe.

The U.S. has repeatedly complained in recent years that Russian planes have flown dangerously close to American aircraft and the two nations routinely shadow each other in international airspace.

In this latest incident, in open ocean northeast of the Philippines, the Russian military accused the Chancellorsville of making a dangerous manoeuvre by crossing the path of the Russian destroyer Admiral Vinogradov.

It said in a statement that the U.S. cruiser "suddenly changed direction and crossed the path of Admiral Vinogradov just 50 metres away," forcing the crew of the Russian ship to make a quick manoeuvr to avoid collision.

The Russian military said its navy sent a radio message in protest.

With U.S.-Russian relations at post-Cold War lows over the Ukrainian crisis, the war in Syria and Moscow's meddling in the 2016 U.S. presidential election, the Russian and U.S. militaries have frequently exchanged accusations of what they describe as unsafe manoeuvres by the other's warplanes and navy ships.

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Yamaguchi reported from Tokyo; Associated Press writer Vladimir Isachenkov in Moscow contributed to this report