At least 22 people have died and 55 have been injured after four carriages of a train travelling from Moscow to St Petersburg derailed.
A railway spokesman said the accident happened at 9.30pm (6.30 Irish time) near the town of Bologoye 350km from Moscow.
An officer in the regional emergencies office said: 'The figure could grow because the rescue operation continues.'
Russian news agencies quoted transport officials as saying the electricity supply may have been at fault.
However, several witnesses said they heard a loud bang before the train derailed.
The ITAR-TASS state news agency is reporting that the accident could be as a result of an attack.
