A misdirected missile from a Russian cruiser caused the disaster of the Kursk nuclear powered submarine during a training exercise, says a member of a Russian parliamentary team investigating the disaster. Sergei Zhikov, a deputy and a former submariner, said yesterday that the Kursk and the Peter the Great, a Russian cruiser, were on an exercise in the Barents Sea in which "the cruiser acted as an enemy aircraft carrier and the submarine was expected to attack it". He said the Peter the Great fired five anti-submarine missiles at the Kursk but only four could be found afterwards.

"It looks like the submarine was hit by the missing [anti-submarine] missile," Mr Zhikov told the Interfax newsagency.The Kursk then tried to rise to the surface in an emergency but had hit the bottom of the Peter the Great.

The cause of the sinking of the Kursk and the death of its 118 crew is an episode that President Vladimir Putin wants to put behind him. The Kremlin now says that nobody survived the initial explosion and that tapping sounds from inside the hull, which the Russian navy said showed that some sailors were alive 48 hours after the disaster, were made by automatic machinery.

The claim by Mr Zhikov is similar to a report in the Berliner Zeitung newspaper last week, which said that an investigation by the Russian Federal Security Service had concluded that the Kursk had been sunk by a Granit missile fired by the Peter the Great. It said that the Granit had travelled 12 miles underwater before exploding close to the Kursk.

Russian officers have hotly denied that the Kursk could have been sunk by one of their own ships, but have been unable to explain exactly what happened. The Pentagon said that there were two explosions in the vicinity of the Kursk at 7.28am and 7.30am on 12 August.

The second was 45 to 50 times bigger than the first, suggesting that one or more of the Kursk's own torpedoes had exploded. That appears to be confirmed by the extent of the damage to the forward part of the submarine, but the cause of the first explosion is still unknown.

A problem for the Russian authorities is that they have now changed their story so often that what they say carries little credibility. Mr Putin revealed to a meeting of American media personalities in New York last week that survivors had never tapped on the hull of the submarine as claimed at the time of the disaster by senior Russian naval officers. The sounds were from "a mechanical device on board", he said.

Mr Putin's claim is in keeping with the present Kremlin line that all on board the Kursk were killed immediately, which meant no crew member died because of the incompetence of the Russian rescue effort or the failure to call for foreign help quickly enough.

He was also noticeably more forthcoming to the American media gathered in the 21 Club in New York than he was to the relatives of the dead sailors.