The Federal Security Service chief on Saturday confirmed the death of a prominent Islamist rebel who he accused of plotting a bomb attack on a Moscow-to-St Petersburg train that killed 26 people last year.

Alexander Tikhomirov, also known as Said Buryatsky, was among eight rebels killed in a two-day raid in the volatile Caucasus region of Ingushetia in early March, FSB head Alexander Bortnikov told President Dmitry Medvedev.

"Material evidence was found on the scene of the special operation directly connected to the train blast organized by this group of bandits in November last year," Bortnikov said in comments broadcast on Vesti-24.

Islamic militants from the North Caucasus claimed responsibility for the attack on the Nevsky Express and vowed further "acts of sabotage." No major attacks have followed.

But Buryatsky himself had never claimed responsibility for the bombing, and Bortnikov's comments were the first time that he had been directly linked to the attack.

Buryatsky's death is a major victory for the Kremlin in anti-terror campaign in the North Caucasus, where analysts have said an Islamist insurgency appears to be mutating from a grassroots separatist movement toward global jihad.

Violence in the North Caucasus in the form of shootings and suicide bombs, particularly in the Muslim-majority republics of Chechnya, Ingushetia and Dagestan, has escalated over the last year.

Russia's most wanted guerrilla, Chechen-born Doku Umarov, has vowed on Islamist web sites to spread his attacks from the region to other parts of Russia.

Tikhomirov renamed himself Said Buryatsky after his native Buryatia region in eastern Siberia. He became a cleric and spent several years in Egypt, where he learned fluent Arabic, political analysts say.

Last August he claimed responsibility for organizing the deadliest attack in the North Caucasus in the last four years, when a suicide bomber killed at least 20 and injured 138 at a police headquarters in Ingushetia.

Ingushetia's leader, Yunus-Bek Yevkurov, also confirmed reports that Buryatsky had been killed in a gun battle near Nazran, Ingushetia's largest town.

"He was killed, but his place will be taken over by some other ideologue," news agencies quoted Yevkurov as saying.

Last year, Yevkurov almost died in a suicide bomb attack that Russian police suspected was organized by Tikhomirov.

Islamic insurgents have been active in the tiny republic wedged between North Ossetia and Chechnya for nearly a decade.

Political analysts and rights groups say security forces are effectively at war with Islamist rebels, who want to create an independent sharia-based Muslim state across the North Caucasus.