Putin decries 'terrorist attack'
Dozens of people were killed in the blast, which officials blame on a suicide bomber.
Attack comes just before Russian elections
MOSCOW, Russia (CNN) -- Russian President Vladimir Putin has decried a deadly bombing on a commuter train as a terrorist attack aimed at interfering with Sunday's national elections.
Russia's emergency ministry said 41 people were killed in Friday's attack and more than 150 people were wounded, including 20 critically.
"The crime today is without doubt an attempt to destabilize the situation on the eve of parliamentary elections," Putin said on national television.
"I'm certain that they will achieve nothing. The people of Russia will not allow it."
Interior Minister Boris Gryzlov, head of the party backed by Putin in Sunday's polls, vowed to track down the perpetrators, saying: "The ground will burn under their feet."
Russian officials are blaming a suicide bomber for the blast, which occurred during morning rush hour in the south of the country.
The train was near Yessentuki, traveling from Kislovodsk to Mineralnye Vody in Russia's Stavropol region northwest of the Chechen border, when the blast occurred at 7:30 a.m. (0430 GMT) Friday.
Russia's justice minister said the attack was linked to Chechen rebels, who are fighting for a Muslim republic in Chechnya and have claimed responsibility for numerous attacks that have killed scores of civilians.
The Russian prosecutor's office has launched a criminal investigation.
CNN's Moscow Bureau Chief Jill Dougherty said: "The timing is significant because it is just two days away from parliamentary elections in Russia and that always raises the profile of danger in the country.
"There has been concern about terrorism and now we have this attack."
She added that Chechnya had been pushed off the election agenda recently, with economic issues taking center stage. The explosion put the troubled breakaway republic "back on the front pages and TV screens."
The director of Russia's security police force said the bomber, a man, was aided by three women terrorists, two of whom jumped off the train around the time the bomb detonated near the Chechen border.
The third woman was wounded at some point in the attack, the FSB's Nikolai Patrushev said. The bomber, who had grenades strapped to his legs, died in the blast.
The FSB said its investigation had turned up the bomber's remains and a bag or suitcase that contained explosive materials.
The force of the blast blew people out of the train's second carriage, in which the bomb detonated, officials said. The entire carriage was mangled.
Hours after the blast, rescue workers were struggling to pull victims from the mounds of shattered glass and other debris. A small fire in the electrical wiring hampered rescue efforts.
"The train was moving and then there was an explosion with smoke and ash about," witness Gleb Kovalenko told Rossiya state television. "It happened inside the carriage."
The same train route was hit by an explosion September 3, killing six people and wounding dozens of others. Chechen militants were blamed for the attack. Security was supposed to have been improved on the line.
Russian officials prevented a separate terrorist attack Friday in the southern region of Ingushetia, Russian news agency Interfax reported.
Officials detained two women in a car laden with explosives and weapons, suspected of planning a suicide attack, the report said.
CNN Moscow Bureau Chief Jill Dougherty and Correspondent Ryan Chilcote contributed to this report