Russian PM Vladimir Putin has called for tough measures against those behind the bombing of a Moscow-St Petersburg train in which 26 people died, BBC reported.
He said the attack showed the threat to Russia from terrorism remained high.
He was speaking during a TV phone-in, in which he will answer some of half-a-million questions submitted by viewers.
A North Caucasus Islamist group has claimed responsibility for Friday's attack on the Nevsky Express, some 400km (250 miles) north-west of Moscow.
"It is necessary to act in a very tough way against criminals who carry out these kinds of terrorist attacks," said Mr Putin.
"We have done a lot to break the spine of terrorism, but the threat has not been fully liquidated... The threat of terrorism remains very high."
He urged viewers to remain vigilant and alert to the possibility of future attacks.
A website claim on Kavkazcenter.com said the train attack was carried out by the "Caucasian Mujahadeen" on the orders of its leader, Doku Umarov.
The Chechen is described as one of Russia's most wanted rebels, but it was not possible to verify the claim's authenticity.