He added that it was the first time this computerized system had been used on the submarine during the sea trials and that the computer had malfunctioned during tests in the dock.

An expert who requested anonymity suggested that a toxic form of Freon could have been used in the fire suppression system.

He added that there were unmistakable signs of poisoning, which could not have been caused by Freon: "People were collapsing as though they had been shot."

Breathing Freon is generally safe, but if the concentration in the air is high then suffocation can result.

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SUSPECTS IN POLITKOVSKAYA MURDER CASE PLEAD NOT GUILTY

MOSCOW _ The three men charged with involvement in the October 2006 murder of Russian investigative journalist Anna Politkovskaya have pleaded not guilty, a defense lawyer said on Wednesday.

"The defendants said they have nothing to hide and will give all necessary evidence," Murad Musayev said, adding that 98 percent of the indictment consists of "conjectures and assumptions."

The trial, which began on Wednesday, is being held in a closed court after the jury refused to appear in a courtroom in the presence of journalists.

Politkovskaya, who gained international recognition for her criticism of the Kremlin and reports of military atrocities against civilians in the troubled Caucasus republic of Chechnya, was gunned down in an elevator in her Moscow apartment building in what police described as a contract killing.

Three men, a former police officer and two brothers from Chechnya, have been charged with involvement in the murder. Sergei Khadzhikurbanov and Dzhabrail and Ibragim Makhmudov have been in custody since last August. Investigators have provided no details as to their alleged roles in the crime.

The man suspected of pulling the trigger, Rustam Makhmudov _ the eldest of the Makhmudov brothers _ remains at large.

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MUSCOVITE KILLED AFTER BETTING LIFE ON GAME OF BACKGAMMON

MOSCOW _ A 35-year-old Muscovite has admitted to murdering a visitor to his flat who agreed to stake his life on a game of backgammon, Russian media have reported.

Sergei Smirnitsky was arrested in south Moscow on murder charges after reportedly knocking on his neighbor's door to ask him to help drag a corpse from his eighth-floor flat to the street. The shocked neighbor called the police instead.

The story began when Smirnitsky and his victim-to-be, 23-year-old Vasily Lobozov, agreed to share a taxi together. During the ride, Smirnitsky invited his new acquaintance to come to his flat, and Lobozov agreed.

Upon their arrival, Lobozov noticed and remarked upon a backgammon set sitting on the shelf.

"I made that in the labor camp," said Smirnitsky, who had earlier served time for robbery. "It took me years."

"Shall we play a game?" his guest replied.

Smirnitsky, who was reportedly in a dark mood following the recent death of his brother, then informed his guest that, "With that backgammon set you can only play for dough."

When Lobozov replied that he had no money, his host answered: "Then stake your life."

Lobozov, who presumably did not take the proposal seriously, agreed, and the two men sat down to play. Fifteen minutes later, after Smirnitsky had beaten his young opponent, he went into the kitchen, chose a knife, and plunged it five times into Lobozov's neck.