Russian long-range bombers have flown over the Atlantic and Pacific oceans in a military drill, say Russian media.

A Russian air force spokesman said several pairs of bombers were in the air "accompanied by Nato planes," Itar-Tass news agency said.

Nato said it was aware of the flights but had no comment on whether the Russian bombers had been accompanied by Nato planes.

Last week Russian bombers flew close to the US Pacific island of Guam.

The flights, believed to be the first since the Cold War ended, came as Russia stresses a more assertive foreign policy, correspondents say.

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Itar-Tass quoted Russian air force spokesman Alexander Drobyshevsky as saying: "At present, several pairs of Tu-160 and Tu-95MS aircraft are in the air over the Atlantic and Pacific oceans, which are accompanied by Nato planes".

In last week's flight near Guam, the Russian pilots "exchanged smiles" with US fighter pilots who scrambled to track them, a Russian general said.

The US military confirmed the presence of the Russian bombers near Guam, home to a large US base.

Russian bombers have also recently flown close to US airspace over the Arctic Ocean near Alaska.

Russia is using its booming oil and gas revenues to revamp its armed forces.