A US Air Force F-22 Raptor jetReuters

The US air force launched two American fighter jets after six Russian military planes were detected approaching the US coastline, officials said.

The F-22 jets intercepted the Russian aircraft about 55 miles from the coast of Alaska on Wednesday evening, a spokesman for the North American Aerospace Defence Command (Norad) said.

Norad is a joint American and Canadian command unit, responsible for defending the airspace around North America.

"We do not see these flights as a threat," said John Cornelio, a spokesman for Norad.

The Russian planes were identified as two IL-78 refuelling tankers, two MiG-31 fighter jets, and two Bear long-range bombers, he said. They looped south and returned to their base in Russia after the jets were scrambled from an air force base in Alaska.

Russia tests US airspace limits

Russian Air Force MiG-31 Fighter Jet
Russian Air Force MiG-31 in flight.Dmitriy Pichugin

Lieutenant Colonel Michael Jazdyk said the fighter jets were scrambled "basically to let those aircraft know that we see them, and in case of a threat, to let them know we are there to protect our sovereign airspace".

The US and Russia are at odds over the conflict in Ukraine, where Russian-backed separatists have been fighting for control of parts of the former Soviet state.

In the past five years, jets under Norad's command have intercepted more than 50 Russian bombers approaching North American airspace.

On Thursday morning, two Canadian CF-18 fighter jets intercepted two Russian long-range bombers about 40 miles off the Canadian coastline in the Beaufort Sea.

In both incidents the Russian planes entered the North American Air Defence Identification Zone, which extends about 200 miles from the coastline.

They did not enter sovereign airspace of the United States or Canada.