Four carriages of the luxury train travelling from Moscow to St Petersburg were derailed at 9.30 pm (1830 GMT) near the town of Bologoye some 350 km (200 miles) from Moscow.
“Twenty-two people were killed, 55 were injured,” said a duty officer at the Emergencies Ministry.
“A one metre-diameter hole has been found next to the railway track. Witnesses heard a loud slap before the accident. All of this could point to a possible act of terrorism,” Interfax news agency quoted an unnamed source in Moscow’s law enforcement agencies as saying.
“We are told this could have been a terrorist act,” an official at Russian railways said on condition of anonymity.
Earlier Russian news agencies quoted transport officials as saying the cause may have been an electrical fault.
President Dmitry Medvedev was immediately informed about the accident and Russian railways chief Vladimir Yakunin rushed to the scene. A Kremlin spokesman said Medvedev spoke to Yakunin.
“The head of the state told the director of FSB federal security service Alexander Bortnikov and Prosecutor-General Yuri Chaika to take all necessary steps to investigate the accident,” the spokesman said.
Transport officials said trains were being diverted along alternative lines on one of Russia’s busiest routes.
In 2007, 30 people were injured when the same Nevsky Express train was derailed after an explosion damaged rails.
A group of suspects are now being tried for that attack in the northwestern city of Novgorod. They are suspected of links to a leading Chechen rebels, Doku Umarov.
Once frequent attacks in Russia have declined dramatically since Moscow largely subdued an Islamist insurgency in the troubled North Caucasus province of Chechnya.
