Russian investigators confirmed that Friday's derailment of the Nevsky Express was caused by a bomb. Photo by FPA/BGNES
A North Caucasus Islamist group has claimed responsibility for a bomb that killed 26 people on a Moscow-to-St Petersburg train, a website says.
The website claim on Kavkazcenter.com said last Friday's attack was carried out by the "Caucasian Mujahadeen" on the orders of its leader, Doku Umarov.
He is described as one of Russia's most wanted rebels, but it was not possible to verify the claim's authenticity, the BBC reported.
Moscow had earlier described the Nevsky Express attack as an act of terrorism.
Doku Umarov, a Chechen, is considered the leader of the Islamist insurgency in the North Caucasus. He says he is fighting to expel Russian forces, and to turn the region into an Islamic emirate.
Wednesday's web statement said Friday's attack was an "act of sabotage", and part of a series of operations targeting strategic sites in Russia.