BISHKEK, Kyrgyzstan — Kazakhstan’s powerful intelligence agency said on Saturday that it had arrested Karim Masimov, who only days before was the agency’s leader, on suspicion of treason.
Mr. Masimov has been regarded as a key ally of the former long-serving president, and the announcement seemed to be another sign of the infighting among the country’s political elite that appears to have contributed to this past week’s violence.
The intelligence agency, a successor to the Soviet K.G.B., said in a statement that Mr. Masimov was arrested on Thursday, a day after the Kazakh president, Kassym-Jomart Tokayev, dismissed him from his post, replacing him with the head of his own security detail. The agency also provided no details of what the government was basing its accusations of treason on.
Several other officials were also arrested, the statement said, but it did not identify them or give any further details.
Kazakhstan, the world’s largest landlocked country, was plunged into crisis this past week after protests over a fuel price hike in a remote western oil town suddenly spread thousands of miles east, to Almaty, its biggest and most prosperous city.
As the protests grew, Almaty was turned into something like a war zone. Dozens of protesters and some security officers were reported to have been killed, and videos showed blackened, burned-out government buildings and the shells of incinerated cars. The Kazakh authorities said that more than 4,000 people had been detained.
At a critical point during the upheaval, Mr. Tokayev formally requested that the Collective Security Treaty Organization, a Russia-led military alliance, intervene. Russia, along with other countries that belong to the organization, sent up to 2,500 troops to help the Kazakh authorities quell the unrest.
In a phone call with President Vladimir V. Putin of Russia on Saturday, Mr. Tokayev expressed his “special gratitude” to Russia for its help, a Kremlin statement said.
It is difficult to assess exactly what is happening inside Kazakhstan, which has been largely sealed off from the outside world. Its main airports are closed or commandeered by Russian troops, while internet services and phone lines are mostly down.
The announcement of Mr. Masimov’s arrest comes amid continued signs of the infighting among the country’s political elite that is believed to have contributed to the chaos.
Mr. Tokayev moved this week to virtually sideline Kazakhstan’s first president, Nursultan Nazarbayev, who had retained wide powers as the head of the country’s security council, an umbrella group for national security coordination, and was given the honorary title of “people’s hero.”
At the height of the tumult on Wednesday, Mr. Tokayev — whom Mr. Nazarbayev had handpicked as his successor when he stepped down in 2019 — announced that he had replaced Mr. Nazarbayev as the head of that agency, leaving the former president without any formal levers of power.
After the move by Mr. Tokayev, rumors swirled that Mr. Nazarbayev had fled the country. But Mr. Nazarbayev’s spokesman dismissed them on Saturday, saying that the former leader was in the capital, Nur-Sultan, and that he was urging Kazakhs to find a way to support the president.
Understand the Protests in Kazakhstan
Mr. Nazarbayev “calls on everyone to rally around the president of Kazakhstan to overcome current challenges and ensure the integrity of the country,” his spokesman, Aidos Ukibay, wrote on Twitter.
The announcement on Saturday, that Mr. Masimov, long a Nazarbayev loyalist, was now being accused of treason added to the considerable intrigue around the infighting among the country’s elite and how it was playing into the unrest.
Mr. Masimov, who at one time served as Mr. Nazarbayev’s chief of staff and as Kazakhstan’s prime minister, twice, has been regarded as “a mastodon of Kazakh politics,” said Daniil Kislov, a Russian expert on Central Asia who runs Fergana, a news site focused on the region.
Mr. Masimov has remained close to some of Mr. Nazarbayev’s influential family members, Mr. Kislov said.
“He has been one of the most influential people,” he said, “the ultimate power broker.”