At least 39 people were killed and nearly 100 injured when a Russian express train came off the rails late last night in what the head of the national railway company said could have been a bomb attack.
The Nevsky Express, carrying 661 passengers from Moscow to St Petersburg, was derailed at 9:34 p.m. (1834 GMT) near the village of Uglovka about 200 miles north of Moscow.
A Reuters photographer saw soldiers carrying four body bags away from the scene where rescue workers cut through the tangled steel to search for survivors in two wrecked train carriages.
"There is objective evidence that... a blast from an explosive device is one of the explanations for the Nevsky Express incident," Russian Railways chief Vladimir Yakunin told reporters at the scene.
A spokesman for Russia's main domestic intelligence service, the FSB, declined to comment on whether an attack was suspected, saying merely that investigators were at work.
Emergencies Minister Sergei Shoigu was told by a ministry official on a video conference shown live on Vesti-24 state television that the death toll had risen to 39 after more bodies had been pulled from wrecked carriages.
Ministry officials later said only 25 people had been confirmed as dead, though they said the toll could rise and that at least 18 people were still unaccounted for.
The derailment is Russia's worst train accident for years and talk of sabotage is likely to raise fears of an upsurge in attacks on the Russian heartland by rebels from the North Caucasus.
President Dmitry Medvedev has been informed about the derailment which has delayed 27,000 people as transport officials tried to divert trains along smaller lines.
Interfax news agency said a three-foot wide crater had been found next to the railway track, though Reuters reporters at the scene did not see one.
A railway official who asked not to be named said a witness had reported hearing a loud bang, though another passenger told reporters in St Petersburg there had been no blast.
After a blast on August 13, 2007 that derailed the Nevsky Express and injured at least 30 people, prosecutors arrested two residents of Ingushetia and charged them with helping to carry out the attack.
Russian prosecutors said they believed ex-soldier Pavel Kosolapov, a former associate of the late Chechen rebel leader Shamil Basayev, was the mastermind behind the blast. Kosolapov is still on the run.
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."