Security has been increased across the North Caucasus after an explosion on a commuter train near Chechnya, in which 40 people died and about 150 others were injured. Russian President Vladimir Putin blames terrorists for the bombing, and vows to punish the culprits.
President Putin says Friday's attack, during the early morning rush hour, shows that terrorism remains a major threat to Russia.
Mr. Putin says terrorism is a cruel, insidious and dangerous enemy that takes innocent lives. He vows that the Russian government will do all it can to help the victims and their families.
President Putin also said the attackers will not achieve their apparent aim of disrupting this Sunday's scheduled parliamentary election in Russia, in which parties loyal to the Russian president are expected to win.
Mr. Putin made the comment during a meeting with the head of Russia's Federal Security Service, Nikolay Patrushev. Mr. Patrushev revealed some new details from the investigation, as reported by Russian television.
Mr. Patrushev says investigators have learned that three women organized the attack, two from directly inside the train. He says the two women jumped out of the windows just before the explosion, while a third is believed to have controlled the attack from a nearby car.
He said one of the women was seriously injured in the attack and is not expected to live.
Mr. Patrushev says a man with grenades attached to his legs is also believed to have been involved. His body was found at the scene, as investigators dug through the wreckage.
The force of the blast was estimated to be equal to 10 kilograms of TNT.
Russia has been hit by a series of bombings and suicide attacks, which the government usually blames on Chechen separatists.
But in a statement to the news media, the rebel Chechen government led by Aslan Maskhadov denied responsibility.
The Council of Europe called the attack a despicable act, and said it will achieve nothing for the terrorists behind it. Several human rights group in Russia also spoke out against the violence, calling it a barbaric act without justification.