A bomb derailed a passenger train heading from the capital of restive Chechnya to Moscow on Sunday and casualties were few only because the bomb was sited at a point where trains slow down to take a bend. The attack was seen by some politicians as an attempt by separatist rebels to overshadow Russia's key national holiday.
The blast, 150 km (90 miles) south of Moscow, left a one-metre-wide (three-feet-wide) crater and derailed, fully or partially, six carriages, Reuters television cameramen at the scene said.
Eight people were taken to hospital with injuries, Interfax news agency quoted medical officials as saying. A further 34 people suffered lighter injuries.
"According to the initial reports, the train had been derailed by a blast of an explosive device equivalent to 3 kg (6.6 lb) of TNT," a spokesman for FSB security services said. Interfax news agency earlier quoted deputy governor of the Moscow region Alexei Panteleyev as saying the power of the bomb was equivalent to 5 kg (11 lb) of TNT.
But he said the effect of the explosion had been reduced because the bomb was planted at a location where the railway line turns and trains slow down.
RIA news agency quoted FSB officials as saying the bomb went off right in front of the train engine. Officials also said investigators had found wires leading to the crater and a remote control device some 50 metres away.