MALAYA VISHERA, Russia, Aug 13 (Reuters) - An explosion derailed a Russian train travelling between Moscow and St Petersburg on Monday, injuring dozens of passengers, officials said.
Russian Railways said in a statement the blast was caused by "outside action", suggesting it may not have been a technical fault. No other details were given.
Interfax news agency quoted law enforcement sources as saying a crater measuring about 1.5 metres (5 ft) in diameter was found underneath one of the carriages.
"The (train) driver said he heard a loud bang," Alexander Pirkov, an adviser to Russian Railways head Vladimir Yakunin, told the Vesti-24 television news channel.
The derailment occurred in the Novgorod region, about 500 km (310 miles) north of Moscow, near the village of Malaya Vishera. The line between Moscow and Russia's second city of St Petersburg is among the country's busiest.
"As a result of an explosion at 21:38 (1738 GMT) ... several carriages of passenger train No. 166 from Moscow to St Petersburg were derailed," said Russian Railways.
Russia has a history of violent attacks on civilian targets, many carried out by groups linked to a separatist insurgency in the southern Chechnya region. But no major attacks have been launched outside Chechnya and neighbouring regions for at least a year after many insurgents were either killed or arrested.
A Reuters Television producer at the scene said police had cordoned off the crash site and that she could see several ambulances. A Reuters photographer who was able to get inside the cordon said he could see at least three derailed carriages.
Officials said 12 carriages and the train had been derailed.
Viktor Beltsov, a spokesman for Russia's Emergencies Ministry, said 27 people were admitted to hospital to have injuries treated. "Three are in a serious condition," he said.
Russian news agencies reported a total of 60 people were hurt but that most did not require hospital treatment.
Russian news agencies reported the line had been closed, but that alternative routes would be put into operation to keep trains running. (Additional reporting by Guy Faulconbridge)