Hope was fading this morning for the crew of 116 on board one of Russia's most prized nuclear submarines, trapped after an apparent collision at the bottom of the Barents Sea, navy officials said.
Russian navy sources told the Itar-Tass agency that the Kursk had probably crashed into a foreign submarine during Sunday's exercises of the Northern Fleet.
The Pentagon quickly dismissed any connection with the accident, stressing there was "no indication that a US vessel was involved in this mishap".
Russia's navy said the nuclear-powered submarine was not carrying any nuclear weapons while in Norwegian waters, and the Norwegian Institute for the Prevention of Radiation said tests showed no initial signs of contamination in waters where the Kursk went down.
Efforts to rescue the crew - reported as 116 in the latest official estimate - began yesterday evening when an air supply pump was lowered from a Russian vessel. However, hours later navy officials told Interfax that stormy seas were seriously hampering their efforts.
"We have thrown all of our rescue forces [to help the Kursk ], but the situation there is serious. The chances of a favourable outcome are not very high," Admiral Vladimir Kuroyedov was quoted as saying. "There are signs of a major and serious collision."
Since Sunday the submarine has been stranded under 100 metres of water some 100 km north of Russia's Severomorsk port. A source at the Northern Fleet said that the authorities "cannot rule out casualties among the crew". Reports said the vessel was starting to flood, lying on one side with the front section already completely flooded.
"If they don't rescue them within the next 48 hours I don't think they will survive," Mr Paul Beaver of Jane's Defence Weekly said in London.
It was not clear whether the Kursk was in radio contact with the navy since the accident. Navy sources told Itar-Tass that rescue services were communicating with the crew members by banging on the outside of the vessel. The Interfax news agency, however, cited the Northern Fleet press service as saying radio contact had resumed yesterday.
One of the most modern submarines in the Russian navy, the Kursk shut down the main nuclear reactor propelling its engines early on Sunday, hours after it took part in the military exercises.
An Oscar-class vessel under NATO specifications and weighing 17,000 tonnes, it came into service in 1995 with the capacity to function for 120 days at depths of up to 500 metres. Echo Moscow radio, citing military experts, said the submarine had enough oxygen to survive an emergency situation for eight days.
Preliminary surveys at the bottom of the Barents Sea ruled out a collision as cause of the disaster, Itar-Tass quoted a defence company source as saying late last night. The agency said its source was an official at a defence firm taking part in efforts to rescue the submarine. The source "did not exclude the possibility that the damage to the nose section of the sub was caused by an explosion in that section", Tass said.
But the agency also noted it had earlier quoted an official with Russia's Northern Fleet as saying that a collision perhaps with a foreign submarine was considered the "key version".
The United States is ready to help Russia with its crippled submarine, the White House spokesman, Mr Joe Lockhart, said in Los Angeles yesterday. "But at this point, there has been no request," he added.