AN international rescue operation was last night in a race against time to reach a stricken Russian mini-submarine before its oxygen supplies run out.

Aircraft from Britain and the US were flying to Kamchatka, in the Pacific, with remote-controlled underwater vehicles to join attempts to rescue the seven sailors on board.

But it was unclear whether there would be enough oxygen aboard the submarine to keep the crew alive long enough for the unmanned craft to reach them.

Pacific Fleet commander Admiral Victor Fyodorov was quoted as saying that the supply would last until Monday.

But he earlier told Russia's Channel One television that the air would last "a little more than 24 hours".

Naval authorities were trying to figure out how to raise the mini-sub, called an AS-28, from the seabed where it got caught on a fishing net at a depth of about 190 metres.

Amid conflicting reports, one source said that a Russian rescue vessel had attempted to snag the mini-submarine - designed for three crew members - with a cable to drag it to shallower waters.

Earlier, Admiral Fyodorov said on state television that the sub was being towed. But navy spokesman Captain Igor Dygalo later said that tension was noted on the cable, but it could not be confirmed that the vessel had been snagged.

"There is air remaining on the underwater apparatus for a day - one day," Capt Dygalo said.

"The operation continues. We have a day - and intensive, active measures will be taken to rescue the AS-28 vessel and the people aboard."

The vessel's propeller became entangled in a fishing net on Thursday, trapping the craft, he added.

The mini-submarine is trapped in Beryozovaya Bay, about 47 miles south of Kamchatka's capital, Petropavlovsk-Kamchatsky.

It became disabled after it was launched from a ship in a training exercise. It was too deep to allow the sailors to swim to the surface or for divers to reach it, officials said.

The sailors were in contact with authorities and were not hurt, Pacific Fleet spokesman Captain Alexander Kosolapov said.

The British Scorpio submarine was last night loaded onto an RAF C-17 transport aircraft, which took off from Scotland's Prestwick airport.

It is expected to arrive early today, ahead of the two US Navy robotic rescue vehicles, which were being flown from San Diego, California.

It will be the first time since the Second World War that a US military plane has been allowed to fly to Kamchatka.

Japan has also dispatched a vessel carrying rescue gear and three other ships to join salvage efforts.

The accident occurred almost exactly five years after the nuclear submarine Kursk sank to the bottom of the Barents Sea after explosions on board, killing all 118 seamen in a painful blow to the Russian navy.