The submarine, a November class K-159, was on its way to be stripped of its nuclear reactors when it sank about three miles off Kildin Island, in heavy seas.

Only one member of the vessel's 10-man crew has been rescued. Two bodies have also been recovered.

President Vladimir Putin - currently on a visit to Italy - has promised "a thorough investigation" into the incident.

"At the moment we are considering the various ways of raising it," Russia's Navy chief-of-staff, Viktor Kravchenko, told the NTV television channel.

"We will definitely raise it so it can be destroyed."

But some Russian military experts have expressed doubts about the feasibility of salvaging the submarine, saying Russia does not have the necessary resources to accomplish the operation.

Rescue efforts are still going on, but Mr Kravchenko said that "the hopes of finding alive the missing are very slight".

It would keep us busy for no less than two years to lift a submarine from that depth - we have no resources for this kind of work Yuriy Senatskiy Russia's rear admiral

A Russian military prosecutor has opened an inquiry into the incident.

The submarine's two nuclear reactors were shut down in 1989 and Russian officials said there were no weapons on board the vessel and no danger of nuclear contamination.

Norway has said there was no sign of any radiation hazard from the stricken submarine.

"There is no immediate radiation danger to the atmosphere or sea, so there is no cause for concern," Norway's radiation protection authority told the AFP news agency.

The incident comes three years after Russia's worst peacetime naval disaster when all 118 crew of the nuclear submarine Kursk died when it sank in the Barents Sea on 12 August 2000.

When the Kursk sank, Russia's government and military were slow to admit what had happened, and slow to ask for foreign help in the search for survivors.

Fierce storm

This caused an avalanche of protests both in Russia and abroad, seriously denting the popularity of President Putin and the government.

The BBC's Damian Grammaticas says that this time at least the government has released information promptly and the navy's chief-of-staff has already flown to the scene to oversee an investigation into the accident.

The submarine sank at 0400 local time (0200 GMT) about three miles off Kildin Island.

K-159 NUCLEAR SUB November class sub Up to 86 crew Can carry two nuclear reactors Can be armed with low-yield nuclear torpedoes Subs of this class entered service in late 1950s Sources: Jane's Fighting Ships, Danish experts

A spokesman for the Northern fleet said the vessel was being towed on four floating hulls from its base in the town of Gremikha to a plant in the town of Polarnoye to be scrapped.

He said the vessel became unstable after one of the hulls was torn off in the fierce storm and then sank in waters 170 metres deep.

Experts have already questioned the navy's ability to salvage the vessel from the seabed.

"It is scrap metal and nothing more. It would keep us busy for no less than two years to lift a submarine from that depth," Russia's rear admiral Yuriy Senatskiy told Moscow's Echo Moskvy radio station.

"Moreover, a stormy season is coming. We have no resources for this kind of work. The Kursk has demonstrated that we are absolutely helpless in such matters," he added.

'Rotting fleet'

Since the collapse of the Soviet Union in 1991, Russia has decommissioned about 190 nuclear powered submarines.

But experts say more than half of them still have nuclear fuel in their reactors.

The submarines spend years sitting in berths, their hulls rusting, often getting inadequate maintenance.

The Russian Government cannot afford to keep them, but it also cannot afford to dispose of them safely, without international assistance.