more than a decade after the end of the Cold War, Russian and NATO submarines are still playing a tense game of cat and mouse under the Barents Sea, defence experts said yesterday.
Fewer Russian vessels put to sea as a result of military spending cuts, but the stretch of icy water on the edge of the Arctic Ocean remains a dangerous stalking ground.
"The Cold War has not ended under the ice," said Mr Paul Beaver, a defence expert with Jane's Defence Weekly. "They follow each other, they track each other and they play with each other," he said. Experts said NATO submarines were almost certainly in the vicinity when the Kursk, a 14,000-tonne Oskar-class submarine, sank to the bottom of the sea.
However, defence analysts ruled out the possibility of collision between the Kursk and a NATO vessel, saying it was "very unlikely".
Tracking the Russian submarines on exercises in the Barents Sea provides an opportunity for NATO to amass intelligence on the latest vessels and their capabilities.
The detente between Russia and the West after the dissolution of the Soviet Union did little to ease the tension under the sea.
"It still goes on," said Ms Joanna Kidd, a naval specialist at the International Institute for Strategic Studies, near London.
"It is on a very much reduced level and the main reason is that really there are hardly any Russian submarines putting to sea," she added.
NATO's planned expansion into Eastern Europe - which Russia perceives as a threat to its security - has given a new edge to the standoff, said Prof Margot Light, chair of the Centre for International Studies at the London School of Economics.
"It would be very surprising if there were no American submarines in the area," she said.
But analysts agreed that it would be very hard for a Russian and NATO submarine to run into each other. "It really should not happen," said Ms Kidd. "They are hunting for each other, so to collide is a huge error on the part of both of them.
"It is more likely that the submarine collided with a Russian vessel because there were about 30 ships and submarines taking part in the exercises." Meanwhile, naval analysts said the most puzzling aspect of the incident was the apparent inability of the crew to communicate with the outside world.
The submarine would have been equipped with low-frequency radios and underwater telephones and signals equipment, as well as communication buoys designed to be released in the event of a serious accident, experts said.
Yet in scenes conjuring up episodes from second World War films, the stricken crew were forced to communicate with their potential rescuers by tapping on the hull in morse code, according to Russian navy reports.
"It is very confusing, almost doomsday-like," said Commander Jeff Tall, a former captain of the Polaris submarine HMS Repulse. He said the Kursk should have had a battery-powered underwater phone system with a range of three miles.
"The Kursk was a strong submarine. Whatever caused the accident, there was a lot of energy behind it," said Mr Mike Finney, a former commander of a British nuclear submarine. He added that the Russians were no novices when it came to underwater engineering and oceanography.
There was increasing speculation yesterday that Saturday's accident was caused by an explosion in one of the Kursk's torpedo tubes in the bow, causing a leak which flooded several compartments of the submarine.
The Russian navy commander, Admiral Vladimir Kuroyedov, was quoted by Interfax news agency as saying the investigation into the cause of the accident was now focused on a possible explosion in the front section of the submarine as the crew prepared to fire a torpedo. Officials have played down earlier suggestions that the Kursk collided with a foreign vessel or another object.
Commander Tall said an exploding conventional torpedo seemed the most likely cause of the accident. It would have seriously damaged the front of the boat. A similar blast occurred on a British submarine, HMS Sidon, off Portsmouth in 1955.
In Washington, a Pentagon official said one of the two US navy submarines in the area at the time of the accident reported having heard an explosion on Saturday.