President Vladimir Putin has accused foreign rivals of using radical Islam to weaken the country, a day after a suicide bombing in Russia's Volgograd region.
"Some political forces use Islam, the radical currents within it ... to weaken our state and create conflicts on Russian soil that can be managed from abroad," Putin told Muslim clerics at a meeting in the Russian city of Ufa on Tuesday.
About 1,000km northeast of Volgograd, a female suicide bomber from the mainly Muslim North Caucasus killed six people on a bus on Monday.
Putin did not say which foreign rivals he was referring to.
The bomber was from Dagestan, one of the predominantly Muslim republics in the North Caucasus, according to Vladimir Markin, the spokesman for the Investigative Committee, Russia's main investigative agency.
In a statement released on Monday, Markin identified the suspect as 30-year-old Naida Asiyalova based on identity documents found near the explosion site.
Encouraged to become rebel
The Russian state television showed pictures of Asiyalova's passport.
Rasul Temirbekov, a spokesman for the Investigative Committee's branch in Dagestan, said Asiyalova had a fatal bone illness and was married to an ethnic Russian, Dmitry Sokolov, whom she had met while both were university students in Moscow.
She encouraged Sokolov - also known as Abdul Jabbar - to become a rebel, and he quickly gained a reputation as an expert in explosives, Temirbekov said.
Irina Gogolyeva, a spokeswoman for the Emergency Situations Ministry, said 40 people were on the bus when the explosion occurred on Monday afternoon.
The local government on Monday placed security forces in the Volgograd region on high alert for 15 days.
No one immediately claimed responsibility for Monday's suicide bombing, but it was the first outside the North Caucasus since Chechen rebel leader Doku Umarov called three months ago for a resumption of attacks on civilians and urged armed fighters to target the Winter Olympics, to be held in Sochi in February 2014.
Volgograd is a city of about one million people that lies 900km southeast of Moscow and a few hundred kilometres north of the North Caucasus and the Black Sea resort city of Sochi.