Police experts examine the remains of the car of the Islamic leader of Russia's main Muslim region of Tatarstan following a car blast in Kazan on July 19, 2012. (Roman Kruchinin/AFP/Getty Images)

Assassins on Thursday attacked Russia’s two most prominent Muslim opponents of religious extremism, killing one, in a move that stoked fears the nation’s long, violent struggle against Islamic radicals may be spreading.

Both men were targeted in Kazan, a serene, prosperous city on the Volga River that is the capital of Tatarstan, Russia’s traditional Muslim heartland. Valiulla Yakupov, a deputy mufti, was killed and Ildus Faizov, Tatarstan’s chief mufti, was hospitalized.

Authorities quickly blamed radical Islamists for the attacks, noting that the two men were staunch defenders of their traditional culture and had been engaged in an escalating struggle against Salafi influence among the Tatars. If they are right, it could mark a turning point for Russia and for its Islamist insurrectionists, who until now have mostly focused on terrorist acts in the rugged North Caucasus, far to the south.

It is also likely to fuel Russian alarm over Islamic extremism, already evident in Moscow’s continuing warnings about al-Qaeda’s presence within the opposition to Syria’s President Bashar al-Assad.

Tatarstan, with a population of 4 million, is an important oil-producing region in the middle of Russia. It has been a center of Islamic culture since the 10th century, and it held sway over Moscow until Ivan the Terrible turned the tables and conquered Kazan in 1552.

Yakupov was shot dead in the lobby of his house as he was leaving for work. “He was one of the ideological leaders of Tatar Muslims,” said Alexei Malashenko, of the Carnegie Moscow Center. Faizov, his superior, was thrown from his car by an explosion about an hour later. Both his legs were broken, but he is expected to survive.

“They wanted to defend traditional Russian Islam against extremists and radicals,” said Mukhamedgali Khuzin, head of the Central Spiritual Board of Muslims of Russia. “Law enforcement agencies should finally wake up. There should be no negotiations with extremists. You should fight this ideology based on hatred with arms, not words.”

Russia fought two wars against Chechen separatists in the 1990s, and radical Islamists have been especially active in neighboring Dagestan, where at least five imams have been killed in the past 13 months, and more than 50 since the 1990s. A replay of Dagestan in Tatarstan would be a nightmare for Russia.

Roman Silantyev, a Christian scholar and expert on Muslim issues in Russia, said the nightmare is at hand. “This is the beginning,” he said, “of a total war against Islam in Russia” — by Islamists.

The Volga region has been calm up to now. But Eduard Ponarin, an expert on Russian Muslims in St. Petersburg, said that when violence begins, it can accelerate rapidly. “The authorities are bound to do something, and then the Salafis will respond, and it can get very bad,” he said.

In Moscow, Russian President Vladimir Putin told a group of lawmakers: “It’s a serious signal. We have on the whole been aware of what’s going on in some Russian regions, but being aware is not enough. It is necessary to understand the situation, analyze it and make timely decisions.”

After the Soviet collapse, Saudi missionaries preached their brand of puritanical Islam among a Tatar population that had maintained only the most tenuous ties to religion after 70 years of communism. The Tatars had developed a theology over the centuries that stressed rational thinking and tolerance — living, as they did, side by side with Orthodox Christian Russians — and that venerated ancestors and saints. To Salafis, that is anathema. And, largely ignorant of their own cultural past, many young Tatars have been drawn to the simplicity of Salafi Islam.

Top muslim leaders attacked in Russia (Laris Karklis/The Washington Post)

They think of it as a “complete” religion — that is, perfect, unevolving, unquestionable. And they consider the traditional Muslim establishment to be hopelessly compromised by its association with first Soviet, and then Russian, political authorities. One imam, in the city of Almetyevsk, in easternmost Tatarstan, contemptuously referred to the religious leaders in Kazan as “mullah-crats” during a 2010 interview.

No imam openly advocates violence in Tatarstan, and even the most radical say they are trying to help Tatars recover their own religion. “Today they are soft and mild,” Rafik Mukhametshin, the head of the Islamic University in Kazan, said, also in 2010. “Tomorrow they will pick up guns and start shooting.”

Faizov and Yakupov drew criticism, even from establishment Muslims, because of their warnings about potential terrorists in their midst, Silantyev said. “Yakupov has given his life now for that.”

Yakupov, over the years, had been especially alarmed by the appeal of the “pure” Islam of his opponents. Trained as a chemist, he once told Danis Garayev, the editor of a Web site on Islam in Kazan, “I understand there is no such thing as a pure substance.” Ponarin called him “pragmatic, very able, and even cunning.”

A key moment may have been a showdown over Faizov’s effort in April to remove a popular imam from a mosque in Kazan. He and Yakupov received death threats, and finally the political authorities told them to back off. That, Khuzin said, only emboldened the radicals supporting the imam.

Ponarin said the religious leaders in Kazan now have to choose between clinging ever more closely to the political establishment and deepening their claim to moral authority by distancing themselves from secular power and adopting a more conservative approach to their religion.

However they choose, the political leaders are certain to crack down on anyone they perceive to be a religious extremist. The results may not be what they want. “This is the process of the activation of Islamic radicalism,” said Malashenko.