MOSCOW - At least 25 people have been killed and 87 others injured in a derailment of a Russian express train on Friday, local media quoted emergency officials as saying.

Paramedics wait at Moskovsky train station in St. Petersburg November 28, 2009. Twenty-two people were killed and 55 more injured when a Russian train crashed on Friday, in what officials said could have been an act of terrorism. Four carriages of the luxury train travelling from Moscow to St Petersburg were derailed near the town of Bologoye some 350 km (200 miles) from Moscow. [Agencies]

Four carriages of the Nevsky Express traveling from Moscow to St. Petersburg went off the tracks at 9:30 p.m. Moscow time (1830 GMT) near the town of Bologoye on the border between the Tver and Novgorod regions, Russian Railways said.

Local TV showed that an emergency official at the scene of the incident told Emergency Situations Minister Sergei Shoigu in a video link that up to six persons may remain under the debris. The official warned that the death toll might grow.

Russian Railways said the reason behind the accident was not yet clear, but the derailment could have been caused by an act of terrorism.

The Interfax news agency cited an unnamed source with Moscow's law enforcement agencies as saying that a one meter-diameter hole was found near the scene of the accident.

"Witnesses heard a loud bang before the accident. All this could point to a possible attack," the source said.

A bomb attack hit the same line in 2007, injuring dozens of passengers.

Russian President Dmitry Medvedev has instructed Shoigu to take all necessary measures to extend assistance to those affected, the Kremlin said.

Medvedev has also ordered federal security service FSB chief Alexander Bortnikov and Prosecutor-General Yuri Chaika to investigate into the cause of the disaster.

Russian Railways President Vladimir Yakunin rushed to the scene, where ambulances, rescuers, FSB officers, law enforcers, and railroad specialists are working.

Injured passengers have been sent to hospitals in nearby towns, Russian Railways said. Those not injured left the site by cars, buses and another train heading for St. Petersburg.

The railroad monopoly said trains will move along a bypass route to keep railroad communication between the two largest Russian cities running.

The route between Moscow and St. Petersburg, Russia's second biggest city, is heavily traveled by tourists and business people.

The 14-carriage train was carrying 633 passengers and 20 railway personnel, the emergency situations ministry said.