Russian authorities launch­ed­ an investigation into a possible­ terrorist attack yester­day after an express train carrying hundreds of passengers from Moscow to St Petersburg derailed, killing at least 39 people and injuring scores of others.

The state-run railway company said the derailment late on Friday night could have been the result of sabotage, raising fears that the luxury train, popular with business executives and government officials, was the target of a terrorist attack.

The last three cars of the 14-car Nevsky Express derailed in the Tver province northwest of Moscow, the Emergency Situations Ministry said. Minister Sergei Shoigu said yesterday that 39 people were dead and 18 missing.

Health minister Tatyana Golikova said 95 people were being treated in hospitals.

State-run Vesti-24 television showed grainy footage hours after the derailment of a dented passenger carriage flipped on its side, lying across the tracks. A reporter called the wreck a "terrible catastrophe", saying he was looking at a "warped" carriage and could see other damaged cars as ambulances drove in and out of the cordoned-off site.

Russian Railways said the cause was not yet established but one possibility was sabotage. Russian news agencies cited unidentified officials as saying a small crater was found at the site of the wreck, leading to speculation the derailment could have been caused by a bomb blast.

Trains have been the targets of bombers in Russian in the past.

An explosion on the Moscow-St Petersburg line in 2007 derailed a passenger train and injured 27 people. Authorities are searching for a former military officer they believe was behind the blast, but the motive was unclear.

A December 2003 suicide bomb attack on a commuter train near the Russian republic of Chechnya killed 44.

At least 12 people were injured in June 2005 when a bomb derailed a train headed from Chechnya to Moscow.

The 14-car Nevsky Express was carrying 633 passengers and 20 railway workers during its Friday night run to St Petersburg, the emergencies ministry said.

Terrorism has been a major concern in Russia since the 1991 collapse of the Soviet Union, as Chechen rebels have clashed with government forces in two wars.

Violence connected with conflicts in the Caucasus have repeatedly erupted in other parts of Russia in the past decade, including bomb­ings in the Moscow subway and attacks that brought two passenger jets down in 2004.

But Russia has also been plagued by deadly accidents resulting from its deteriorating infrastructure, a high incidence of alcohol abuse and from negligence.

The derailment occurred about 250 miles north west of Moscow and 150 miles south east of St Petersburg.