Foreign aid for crippled sub

Rescue mission: The LR5 arrives at Trondheim, Norway

Russia has asked two Nato countries to help in efforts to rescue the 118 seamen trapped on the disabled nuclear submarine, Kursk.

A British mini-submarine and team of 27 rescuers has been flown out to help Russian teams and Norway is sending a diving ship and crew of 12 to 15 divers.

Sand and silt envelop the capsule causing zero visibility

Russian Navy officer

Russian rescuers, frustrated by bad weather off the Arctic coast, are still trying to dock a capsule with the submarine, which has been lying on the bed of the Barents Sea since an unexplained accident on Saturday.

The Russians say there has been no sign of life aboard the submarine on Wednesday, but that this did not mean that there were no survivors.

Stranded: Kursk commander, Captain Gennady Lachkov

The crew was thought to have enough oxygen until Friday, although the Russian navy has now revised that estimate to nine days - until 25 August.

'Critical' situation

Attempts by rescue capsules to latch on to one of the cargo hatches of the submarine have been frustrated because of strong currents and swirling sand.

"Sand and silt envelop the capsule causing zero visibility," said a navy officer, who declined to be named.

Moreover, the submarine is lying at a sharp angle, making any latching operation more difficult.

One capsule was almost lost during an earlier attempt because of the strong currents.

Now the Russians have begun using a larger version, called the Bester, a 50-tonne machine manned by a crew of two or three and capable of carrying up to 20 evacuees.

'Underwater helicopter'

The sending of the British rescue sub came as Russian authorities, in an about-turn, finally decided they would ask for foreign help.

A graphic taken from Russian TV illustrating the difficulty of the rescue mission

Russian President Vladimir Putin earlier called the situation "critical".

An aircraft carrying the mini-sub and a team of 27 rescuers arrived at Trondheim in Norway on Wednesday afternoon, en route to Murmansk.

The LR5 sub is a 33ft-long craft described as an "underwater helicopter", with a sophisticated camera system and an array of debris-clearing tools.

Its aim would be to hook up with the Kursk's hatch, but it was not clear whether the British craft's fittings would be compatible with those of the Russian navy.

It could also take several days to get the British equipment out to the site of the accident and bad weather could hamper the British team's efforts just as it has hindered Russia's.

A high-level Russian military delegation will talk to Nato on Thursday in Brussels about the rescue operation.

Russian fears

Across Russia, there is growing unease at what is perceived as potentially one of the country's worst maritime disasters in recent times, and criticism of the military's slowness at asking for help from abroad.

Relatives are praying for their loved ones

"I heard that the boat is on the bottom of the sea. They can't raise it themselves, but they're too ashamed to ask anyone, Britain or France, for help. The accident itself is a sign of Russia's decay," one Russian told the BBC earlier on Wednesday.

Analysts say that apart from injured military pride, there may be security worries that led Moscow to hesitate before calling for help.

Independent military analyst Pavel Felgenhauer says that the Russian navy suffers from a pervasive culture of secrecy.

Kursk facts

Launched May 1994

Length 155 metres

Displaces 18,300 tonnes

Armed with guided missiles and torpedoes

Designed to strike against surface forces especially aircraft carriers

Source: Jane's Fighting Ships

"The Russian navy maybe is afraid that if Western aid arrives, Western navy officers will know the weak points of the Oskar-2 submarines," Mr Felgenhauer said.

The submarine - one of the biggest and newest in the Russian navy - has been lying on the sea bed since Saturday at a depth of more than 100 metres.

An explosion is believed to have ripped through a torpedo tube during a military exercise.

Flooding has closed down the front sections of the boat, forcing the survivors to the back.