An express train carrying hundreds of passengers from Moscow to St Petersburg derailed, killing at least 22 people and injuring dozens of others, emergency officials said.
The state-run railway company said the derailment could have been the result of sabotage, fuelling fears of terrorism.
The three rear cars of the Nevsky Express went off the tracks in the Tver province northwest of Moscow, the Emergency Situations Ministry said. Russian Railways said that four cars derailed and said 50 people were taken to two hospitals in the area.
The emergencies ministry said 22 people were killed and 54 injured, citing preliminary information. The RIA Novosti and Interfax news agencies cited unidentified regional law enforcement officials as saying 25 people were dead and 63 injured.
State-run Vesti-24 television showed grainy footage hours after the derailment of a damaged car apparently lying on its side by the tracks. Its 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 determined but one possibility was sabotage, which could mean a bomb or another deliberate action to derail the train and cause casualties.
