A suspected suicide bomber killed at least 41 people aboard a packed commuter train near rebel Chechnya yesterday in what President Vladimir Putin called an attempt to destabilise Russia just before key polls.

The attack caused fury in Moscow, where Interior Minister Boris Gryzlov vowed to hunt down those responsible, calling them "animals" and saying authorities would make the ground "burn under their feet".

The blast struck an early morning train, filled with students and workers, outside Yessentuki station in Russia's southern fringe, as Putin's allies prepared to fight tomorrow's parliamentary elections on a strong law and order platform.

Television pictures showed film of the train's second carriage torn to pieces. Schoolbags, shattered glass and sheets of twisted metal littered the adjacent rail bed.

Justice Minister Yuri Chaika said the attack bore the hallmarks of "Chechen terrorists", but the rebels denied involvement.

"We condemn all terror acts and acts of violence... directed against the civilian population," the separatists said on their Web site www.kavkazcenter.com.

A spokesman for the local administration said 41 deaths had been confirmed. Doctors were treating more than 160 injured.

"No one could tell us what had happened," said a doctor at a Yessentuki hospital. "All they can recall is being thrown about the carriage. The shock waves hurled them against the walls."

Witnesses said the blast shook the surrounding area. "(It) was so strong that it smashed all the windows," an elderly woman said on television. "The cup of tea I was drinking was sent flying. I felt as though I had been picked up and put back down again."

The rebels have increasingly resorted to suicide bombings in Chechnya and the Russian heartland, the attacks often carried out by female relatives of men killed by Russian forces.