MOSCOW -- Five people suspected of killing a top Muslim cleric and wounding another in Tatarstan province were detained Friday, Russian prosecutors said.

Valiulla Yakupov, the deputy to the province's chief mufti, was gunned down Thursday in the regional capital of Kazan. Minutes later, the chief mufti, Ildus Faizov, suffered leg wounds after an explosive device ripped through his car.

Both clerics were known to be critics of the radical Islamist groups that have mushroomed in recent years in this predominantly Muslim Volga River province of 4 million people.

Faizov has also been criticized by media in Tatarstan for allegedly profiting on tours he organized for Muslim pilgrims and for trying to gain control of one of the oldest and largest mosques in Kazan, which receives hefty donations from thousands of believers.

The Investigative Committee said Friday that one of the suspects – Rustem Gataullin, 57 – owned a company that organized hajj pilgrimages, and another one – Murat Galleyev, 39 – heads a religious institution in Tatarstan.

The 49-year-old Faizov became Tatarstan's chief mufti in 2011 and began a crackdown on radical Islamists by dismissing ultraconservative preachers and banning textbooks from Saudi Arabia, where the government-approved religious doctrine is based on Salafism.

The rise in Tatarstan of radical adherents of an austere, puritanical version of Islam known as Salafism has been fueled by the influx of Muslim clerics from Chechnya and other predominantly Muslim provinces of Russia's Caucasus region, where an Islamic insurgency has been raging for years. Last year, Doku Umarov, leader of the embattled Chechen separatists, issued a religious decree calling on radical Islamists from the Caucasus to move to the densely-populated Volga River region that includes Tatarstan.

Islamic radicals from the Caucasus have called for the establishment of a caliphate, an independent Islamic state under Shariah law that includes the Caucasus, Tatarstan and other parts of Russia that were once part of the Golden Horde – a medieval Muslim state ruled by a Tatar-Mongol dynasty.

The other three suspects in the case are Airat Shakirov, 41; Azat Gainutdinov, 31, and Abdunozim Ataboyev, a 36-year-old national of ex-Soviet Uzbekistan. The investigators did not provide any details on their occupation or background.

Earlier on HuffPost: