MOSCOW - Russia has detained four men suspected of organising an assassination attempt on the Islamic leader of Russia's main Muslim region and killing another top cleric, investigators said Friday.
Moscow-based investigators said the main reason for the double attacks in the oil-rich republic of Tatarstan -- often praised for its religious tolerance -- was the clerics' fight against Muslim radicals.
On Thursday the Mufti of Tatarstan, Ildus Faizov, was wounded in a car bomb while his former deputy, Valiulla Yakupov, was shot dead in the region's main city of Kazan in twin attacks.
Russian President Vladimir Putin called the attacks, which have shocked the country, a "serious signal" to the authorities.
"According to the investigation, the main motive of the crime was the professional activity of the victims including their ideological differences with opponents," the Investigative Committee said.
It cited Faizov's "tough stance" against organisations promoting radical Islam in Tatarstan following his election last year.
The four detained are 57-year-old Rustem Gataullin, head of Idel Hajj, a tour operator for Muslim pilgrims; 39-year-old Kazan resident Murat Galleyev; and Tatarstan residents, Airat Shakirov, 41, and Azat Gainutdinov, 31.
The Investigative Committee noted that Faizov had also taken control of "the transfer of money of Idel Hajj", a tour operator organising trips to Mecca for Muslim pilgrims.
That led to a conflict between the mufti and the head of the tour operator, with the latter threatening Faizov, it said.
Russia fears that the radical Islam plaguing the North Caucasus, where militants are calling for the creation of an Islamic state, could spread to its other historically Muslim regions such as Tatarstan on the Volga.