The Russian authorities yesterday disclosed that the stricken Kursk submarine lying at the bottom of the Barents sea had suffered much greater damage than initially believed, making it highly likely that many of the crew, the vessel's commanding officers and other more senior navy officers died instantly last Saturday.
As hopes faded of bringing out any of the 118 crewmen alive, the defence minister, Igor Sergeyev, revived the first theory advanced for the cause of the disaster - a collision with another vessel.
"The scenario in which the Kursk submarine suffered a collision with another object is now the main one," the defence minister said. "Irrefutable data is already available."
At the northern fleet's main base of Severomorsk outside Murmansk last night, senior navy and government officials were examining five hours of video of the sunken submarine taken earlier in the week by an unmanned observation craft before deciding on their next course of action.
The video shows massive and severe damage to the submarine extending from the nose to the conning tower. "The accident happened so quickly we can say it was like a flash," said Captain Igor Dygalo, the navy spokesman.
A reporter from Russia's state RTR television said the film showed that the Kursk suffered severe damage. "Water flooded the front in a flash and the command centre, I mean the hull, was destroyed in a moment," the correspondent said from a ship on the Barents Sea.
"This is tragic news, when so much water gets into the sub, it is impossible to avoid casualties."
Russian sources said the crash theory focused on the notion that the submarine collided with a surface vessel while trying to come up from the depths. Norwegian experts speculated that the disaster was caused by crew error which sent the submarine careering quickly to the sea bed.
American and Norwegian observation ships detected two blasts at the time of the accident last Saturday, the second much more powerful than the first. Some attributed the explosions to a torpedo blowing up inside the submarine and triggering another explosion.
The Norwegian analysts, Bellona, said the first explosion could have been the thud of the submarine hitting the sea bed which then triggered the more powerful explosion of a pressurised storage tank.
"Nobody knows what caused the accident", a British naval source said, but since the Kursk was very strong, it must have been a "high energy accident".
As a British rescue crew with the LR5 mini sub headed towards the Kursk, the Ministry of Defence said the submarine was so badly damaged that one of its escape hatches was unusable. The LR5 rescue sub would aim for the apparently undamaged hatch at the stern of the vessel.
The craft was lying at an angle of 20 degress, less than earlier suggested. "It could have shifted during the week. It seems to be far more upright, that is good news", the sources said. But underwater currents were extremely strong - and have already severely hampered Russian rescue efforts.
Commander Alan Hoskins of the British rescue team told the BBC his team was trying to remain optimistic. "We hope that we will get there and still find that people have survived," he said.
Tony Blair telephoned the Russian president, Vladimir Putin, from Tuscany to express his concern and to stress that Britain was doing everything possible to assist the operation.
Although the Russian public and media are rapidly losing faith in pronouncements from the top brass,with a wave of resentment and disgust sweeping across Russia at the way the authorities have handled the crisis, the theory that there had been a collision was supported by the fact that the submarine's periscopes were raised.
The retired admiral Eduard Baltin, the former commander of the Black sea fleet, blamed the disaster on bad planning, lack of training and incompetence. "The Kursk is designed for the ocean, not for shallow waters," he said. "Where it was manoeuvring and where it perished is completely wild - strong currents and strong winds. You can't carry out torpedo firing there."
He said the submarine would have been forced to surface to try to identify its torpedo targets, but the 108-metre depth of the sea at that point meant its commanders would not have heard another vessel above.
The vessel's commanding officers would normally be in a section just below the conning tower and experts said their chances of survival were minimal. Other senior navy personnel were on board to observe the war games.
Three days of attempts by Russian rescue capsules to dock with the crippled submarine's escape hatches have yielded no results and the British and Norwegian rescue mission is not expected to reach the site until lunchtime tomorrow, almost exactly a week to the hour since the accident occurred.
"The situation is almost catastrophic," said the prime minister, Mikhail Kasyanov.
The revelations of the massive damage raised fears of radioactive contamination from the two 190-megawatt nuclear reactors which powered the submarine. But Norwegian and Russian authorities said no increase had been detected in radiation levels and that contamination was a long-term problem rather than an immediate one.
The Barents sea, Bellona said, was one of the cleanest in the world and the low levels of radiation detected flowed in on the Gulf stream from Britain's and France's nuclear reprocessing plants at Sellafield and Le Hague.