GROZNY, Russia » Ramzan A. Kadyrov, the strongman leader of Chechnya, has been at the center of intrigue surrounding the murder of Boris Y. Nemtsov, a prominent critic of the Russian president, Vladimir V. Putin. So before a busy weekend that included a night out with the boys to watch cage fighting, Kadyrov wanted to clear something up: "I am utterly devoted to Vladimir Putin and ready until the end of my life to resist the enemies of Russia," he wrote on Instagram.

The question these days is not so much Kadyrov’s fealty to Putin, his political patron, but whether Putin’s Faustian bargain to gain stability in Chechnya, where Russia fought two grisly wars to suppress Muslim separatists, has backfired, unleashing a violent and unpredictable despot.

Critics of Putin have warned that he has allowed Kadyrov, 38, to effectively create the Islamic republic that Chechen separatists had dreamed of – albeit one entirely reliant on Moscow for financial support and where Shariah law is selective, not absolute. And, they say, Kadyrov may now be seeking power and relevance far beyond his base in the jagged hills of the North Caucasus.

Unlike in other regions, where local security forces are subordinate to federal authorities, Kadyrov controls his own internal security troops, known as Kadyrovtsy. He is known for ruthlessly eliminating critics at home and abroad. And in Moscow, he is widely resented by the security services for being allowed to operate with impunity.

"The FSB hate Ramzan because they are unable to control him," Alexey Malashenko, an expert on the Caucasus at the Carnegie Moscow Center, said of the successor intelligence agency to the KGB. "He does whatever he wants, including in Moscow. Nobody can arrest members of his team if there is no agreement with Putin."

Nemtsov had recently called attention to the dangers inherent in such a security arrangement. "I cannot understand what Putin expects when arming 20,000 Kadyrovtsy gathered today in the stadium in Grozny," Nemtsov wrote in a Facebook post in December, after Kadyrov led his troops in chants of "God is great!" at a rally in the Chechen capital’s new soccer arena.

"What will happen next?" Nemtsov wrote. "The country is entering a crisis. There is not enough money for anything, including the support of regions. And the unspoken contract between Putin and Kadyrov – money in exchange for loyalty – ends. And where will 20,000 Kadyrovtsy go? What will they demand? How will they behave? When will they come to Moscow?"

While the authorities have produced no evidence that Kadyrov or anyone close to him ordered the Nemtsov killing, investigators have arrested five Chechen suspects, including a former deputy commander of one of Kadyrov’s security battalions. Even allies of Nemtsov who believe the Kremlin is behind his death say the investigation so far has exposed a dangerous rift between chiefs of the security services in Moscow and the brash Chechen leader.

The rift is of Putin’s making. For eight years, he has sanctioned Kadyrov’s iron-fisted rule while seemingly turning a blind eye to assassinations, torture and other human rights abuses. At the same time, the Kremlin bankrolled an expensive rebuilding effort that has transformed Grozny into a glittering Caucasian oasis, and allowed Kadyrov to amass his heavily armed personal militia.

The result, admirers and detractors agree, is an over-the-top political persona the likes of which Russia has never seen: Islamist warlord, Russian nationalist and fierce Putin loyalist – at least for now.

Long tied to the killings of his personal rivals and critics, Kadyrov has emerged in recent months as one of the strongest backers of Putin’s policies in Ukraine, allowing fighters and weapons to flow from Chechnya to support the pro-Russian separatists. He was a leader of a huge "anti-Maidan" rally in Moscow to protest Ukraine’s shift toward Europe, and in January he led a mass demonstration in Grozny after the shootings at the Paris offices of Charlie Hebdo, a satirical French newspaper, denouncing the publication as anti-Muslim.

Posters proclaiming "We Love the Prophet Muhammad" now hang on buildings throughout the city.

On Saturday evening, Kadyrov was in his element, lounging on a plush high-backed sofa in the VIP section of Grozny’s main sports arena, watching mixed martial arts fighters bloody one another in a metal cage.

Wearing a red baseball cap and a jersey from the local Akhmat Fight Club, Kadyrov sat next to Alexander S. Zaldostanov, nicknamed the Surgeon, who is the leader of the Night Wolves, a pro-Putin biker gang in Russia. At times flashing thumbs up, and at other times thrusting his arm in the air triumphantly, Kadyrov yelled encouragement to the young local athletes battling international challengers.

"Hold him!" Kadyrov screamed in Chechen. "Be more confident!" "Go forward!" "Attack!"

Kadyrov does not go in much for mercy. He has been linked to some of Russia’s most jarring, politically charged killings, including that of a prominent investigative journalist, Anna Politkovskaya, in 2006 and of a human rights advocate, Natalya Estemirova, whose colleagues said Kadyrov personally threatened her months before she was abducted outside her Grozny apartment in 2009.

Two of Kadyrov’s bitter rivals in Chechnya’s notorious tribal politics were eliminated in public killings. Ruslan B. Yamadayev was shot to death while sitting in a car in central Moscow in 2008, while his brother, Sulim B. Yamadayev, was killed in Dubai, United Arab Emirates, in 2009. The Dubai authorities issued an arrest warrant for Adam Delimkhanov, a close adviser to Kadyrov.

A former bodyguard of Kadyrov, Umar Israilov, who had documented gruesome torture and other human rights abuses by Kadyrov and his associates, was killed in 2009 in Vienna, where he had fled with his family.

Kadyrov has generally waved off past accusations, and he was similarly dismissive when asked about Nemtsov, a pro-democracy crusader and dogged critic of Putin, who was assassinated just outside the Kremlin walls.

"What? Am I an investigator?" Kadyrov snapped to a reporter as he strode out of the Grozny Coliseum at 1:30 a.m. into a brisk night, surrounded by his phalanx of heavily armed guards.

"Heh!" he said, exaggerating a laugh. "This is a question for the Investigative Committee, for the prosecutor’s office, for the FSB. I don’t know. I am head of the Chechen Republic. I am not a Muscovite."

The uncomfortable questions are not likely to go away anytime soon.

Speculation about Kadyrov’s role began immediately after the authorities announced that they had arrested the five Chechen suspects, including Zaur Dadayev, who served in one of Kadyrov’s security battalions. In a curious posting on Instagram, Kadyrov said he knew Dadayev personally as a "true Russian patriot."

Questions mounted when just a few days later Putin gave a state award to Kadyrov (and to Andrei K. Lugovoi, who was charged by Britain with killing the fugitive Russian intelligence officer, Alexander V. Litvinenko, by poisoning his tea with polonium).

In Chechnya, Nemtsov was perhaps best known for leading a petition drive in 1996 that gathered 1 million signatures to protest the first Chechen war. And given the republic’s history and reputation for violence, skeptics of the government’s investigation say that charging Chechens with his murder is simply too convenient.

Supporters of Kadyrov say that his enemies in Moscow are trying to undermine his relationship with Putin. Kadyrov, in his post on Instagram, accused the United States of trying "to cause chaos and instability in Russia."

Relatives of the suspects insist that they are innocent.

"I know they are not guilty; I know my sons," Zulai A. Gubasheva, the mother of two of the suspects, Anzor and Shagid Gubashev, said in an interview at her home in the town of Malgobek, in Ingushetia, a region bordering Chechnya. Gubasheva is also an aunt of Dadayev, the suspect whom Kadyrov called a patriot.

Human rights monitors in Moscow who visited the suspects in prison say there are signs they may have been tortured, and despite early reports of confessions all now seem to be denying the charges.

Though there are sporadic flare-ups in violence, Chechnya, with a population of more than 1.3 million, has enjoyed relative calm in recent years, a result of Kadyrov’s authoritarian rule and a sustained crackdown on jihadis that has driven many to neighboring Dagestan and Ingushetia, to Syria, or to support the Islamic state.

Portraits of Putin hang on buildings all throughout the rebuilt Chechen capital, often alongside similar portraits of Kadyrov’s father, Akhmad, who became president in 2003 and was assassinated in 2004.

Islam Saidayev, who works in the Chechen government counseling youths against extremism, rejected the idea that Chechens had killed Nemtsov. The opposition leader had invited his own death, Saidayev said, by taking on a system that could not be defeated.

"The Russian Federation is a big train," he said. "Maybe it’s going in the wrong direction, but no one can stop it. Nemtsov stood on the tracks and tried to stop it. Of course, it ran over him."

The arrested men, he said, were being framed: "It’s just settled opinion that anything bad is done by Chechens."

David M. Herszenhorn, New York Times

© 2015 The New York Times Company