At least 22 people have been killed and 54 injured when a train traveling between the Russian capital Moscow and Saint Petersburg derailed.

Four wagons of the Nevski Express linking the two cities came off the tracks late on Friday evening in the Novgorod region, a railway official told the Ria-Novosti news agency.

Russia's state-run Itar-Tass news agency quoted the emergencies ministry and a railway official as saying that 22 people were dead and 54 others injured.

An unnamed security official was quoted by the Interfax news agency as saying that a one meter-diameter (three feet wide) crater was found near the scene of the disaster.

"Witnesses say they heard a loud bang before the accident. This could be proof of an attack," the source said.

Railway officials also told Itar-Tass that "an attack is one of the possibilities" being looked at by the police.

In 2007, a bomb on the same line derailed a train, injuring 60 passengers, with Chechen separatist or ultra-nationalist groups suspected.

SG/SS/MMA