Two Russian bombers approached a US aircraft carrier in the Pacific and were intercepted by American fighter jets, US defence officials say.

The unnamed officials told news agencies that the Russian bombers had flown over the USS Nimitz in the western Pacific on Saturday.

Four F-18 jets escorted the bombers out of the area, they added.

Russia resumed long-range bomber flights last August, in a move regarded as a flexing of military muscle.

Russian officials were not immediately available to comment on Saturday's incident.

It was the first time a Russian bomber had flown over a US aircraft carrier since July 2004.

Meanwhile, Japan has lodged a complaint with Moscow over allegations that a Russian bomber, thought to be one of those involved in the Nimitz fly-over, intruded into Japanese airspace on Saturday.

The incident comes amid renewed tensions between Moscow and Washington over American plans for a missile defence system based in Poland and the Czech Republic.