* Official says 25 killed, 63 injured
* Crash may have been caused by explosion
By Oleg Shchedrov
MOSCOW, Nov 28 (Reuters) - The crash of a luxury train in Russia killed 25 people and injured up to 63 more, an official said on Saturday, and sources suggested it may have been an act of terrorism.
"Twenty-five people died in the accident," an official reported to Emergencies Minister Sergei Shoigu during a meeting televised by Vesti-25 television, hours after the crash.
Several carriages of the Nevsky Express travelling from Moscow to St Petersburg were derailed at 9:30 p.m. (1830 GMT) on Friday near the town of Bologoye, 350 km (200 miles) from Moscow.
Estimates of the number of injured ranged from 55 to 63 while Itar-Tass news agency quoted a spokesman for the regional emergencies authority in the Tver region as saying as many as six passengers could still be buried under wreckage.
Russian railways said the train carried 661 passengers in 13 carriages and that four of them were damaged. Regional prosecutors said two carriages were affected while Vesti-24 television said their correspondent could see three.
There were no official statements about the cause but several sources suggested it may have been the result of an explosion.
"A one metre (3-ft)-diameter hole has been found next to the railway track," Interfax news agency quoted an unnamed source in Moscow’s law enforcement agencies as saying.
"Witnesses heard a loud slap before the accident. All of this could point to a possible act of terrorism."
A railway official, speaking on condition of anonymity, said, "We are told this could have been a terrorist act."
In 2007, 30 people were injured when the same Nevsky Express train was derailed after an explosion damaged rails.
Earlier, Russian news agencies quoted transport officials as saying an electrical fault may have been to blame.
A spokesman for the Prosecutor-General’s investigating committee, urged caution before leaping to conclusions.
"We will only be able to say what has happened after investigators start their work," the spokesman told Itar-Tass news agency.
President Dmitry Medvedev was informed about the accident and Russian railways chief Vladimir Yakunin rushed to the scene. A Kremlin spokesman said Medvedev had spoken to Yakunin.
In Washington, White House spokesman Robert Gibbs said, "We are deeply saddened by the terrible loss of life and injuries resulting from the reported derailment of a train between Moscow and Saint Petersburg."
Russian transport officials said trains were being diverted along alternate lines on one of the country’s busiest routes.
Suspects charged in connection with the 2007 attack are being tried in the northwestern city of Novgorod. They are suspected of links to a leading Chechen rebel, Doku Umarov.
Such attacks have declined dramatically in Russia since Moscow largely subdued an Islamist insurgency in the troubled North Caucasus province of Chechnya.
Health Minister Tatyana Golikova said the injured were rushed to nearby towns.
"Over 20 ambulances are working at the scene and if needed their number can be increased," Tass quoted her as saying.
(Additional reporting by Gleb Gorodyankin in Moscow and Denis Pinchuk in St Petersburg; Editing by Michael Roddy) ((firstname.lastname@example.org; phone: +7 495 775 1242))