Russian President Vladimir Putin for the first time on Thursday acknowledged the presumed death of Wagner mercenary leader and longtime ally Yevgeny Prigozhin in a plane crash on Wednesday.

Meanwhile, a preliminary U.S. intelligence assessment has found that the plane crash presumed to have killed Wagner leader Yevgeny Prigozhin was intentionally caused by an explosion, according to U.S. and Western officials.

One of the officials, who were not authorized to comment and spoke on the condition of anonymity, said that the explosion fell in line with Russian President Vladimir Putin’s “long history of trying to silence his critics.”

The officials did not offer any details of what caused the explosion that was believed to have killed Prigozhin and several of his lieutenants to avenge a mutiny that challenged the Russian leader’s authority.

The details came the same day that Putin, in a meeting broadcast on Russian state television, expressed condolences to Prigozhin's relatives as well as the families of the other victims of the crash.

“This was a person with a complicated fate,” Putin said of Prigozhin. “He made some serious mistakes in life, but he also achieved necessary results.”

Prigozhin notably led a short-lived uprising against the Russian military in June. 

“I’ve known Prigozhin for a long time, since the early '90s," Putin said. "He was a man of complicated fate and he made serious mistakes in his life. He was a talented man, a talented businessman. He worked not only in our country ... but also abroad."

Putin also expressed his "sincere condolences to the families of all the victims" while pledging that an investigation into the crash -- which resulted in the deaths of all 10 people on board, according to officials -- "will be conducted in full and brought to a conclusion."

The founder of the Wagner military company and six other passengers were on a private jet that crashed Wednesday soon after taking off from Moscow with a crew of three, according to Russia's civil aviation authority. Rescuers found 10 bodies, and Russian media cited anonymous sources in Wagner who said Prigozhin was dead. But there has been no official confirmation.

If the deaths are confirmed, the crash would be the most serious blow the group has ever suffered to its leadership. The passenger manifest included Prigozhin and his second-in-command who baptized the group with his nom de guerre, as well as Wagner's logistics chief, a fighter wounded by U.S. airstrikes in Syria and at least one possible bodyguard.

It was not clear why several high-ranking members of Wagner, including top leaders who are normally exceedingly careful about their security, were on the same flight. The purpose of their joint trip to St. Petersburg was unknown.

In all, the other passengers included six of Prigozhin’s lieutenants, along with the three-member flight crew.

At Wagner’s headquarters in St. Petersburg, lights were turned on in the shape of a large cross, and Prigozhin supporters built a makeshift memorial, piling red and white flowers outside the building Thursday, along with company flags and candles.

Numerous opponents and critics of Putin have been killed or gravely sickened in apparent assassination attempts, and U.S. and other Western officials long expected the Russian leader to go after Prigozhin, despite promising to drop charges in a deal that ended the June 23-24 mutiny.

"It is no coincidence that the whole world immediately looks at the Kremlin when a disgraced ex-confidant of Putin suddenly falls from the sky, two months after he attempted an uprising,” said German Foreign Minister Annalena Baerbock, while acknowledging that the facts were still unclear.

“We know this pattern … in Putin’s Russia — deaths and dubious suicides, falls from windows that all ultimately remain unexplained,” she added.

Ukrainian President Volodymyr Zelenskyy also pointed the finger. “We have nothing to do with this. Everyone understands who does,” he said.

Prigozhin was long outspoken and critical of how Russian generals were waging the war in Ukraine, where his mercenaries were some of the fiercest fighters for the Kremlin. For a long time, Putin appeared content to allow such infighting — and Prigozhin seemed to have unusual latitude to speak his mind.

But Prigozhin's brief revolt raised the ante. His mercenaries swept through the southern Russian city of Rostov-on-Don and captured the military headquarters there without firing a shot. They then drove to within about 200 kilometers (125 miles) of Moscow and downed several military aircraft, killing more than a dozen Russian pilots.

Putin first denounced the rebellion — the most serious challenge to his 23-year rule — as “treason” and a “stab in the back.” He vowed to punish its perpetrators, and the world waited for his next move, particularly since Prigozhin had publicly questioned the Russian leader's justifications for the war in Ukraine, seen as a red line.

But instead Putin made a deal that saw an end to the mutiny in exchange for an amnesty for Prigozhin and his mercenaries and permission for them to move to Belarus.

Now many are suggesting the punishment has finally come.

“The downing of the plane was certainly no mere coincidence,” Janis Sarts, director of NATO’s Strategic Communications Centre of Excellence, told Latvian television.

Even if confirmed, Prigozhin’s death is unlikely to have an effect on Russia’s war in Ukraine. His forces fought some of the bloodiest battles over the last 18 months, but pulled back from the front line after capturing the eastern city of Bakhmut in late May. After the rebellion, Russian officials said his fighters would only be able to return to Ukraine as part of the regular army.

The Institute for the Study of War argued that Russian authorities likely moved against Prigozhin and his top associates as “the final step to eliminate Wagner as an independent organization.”

Abbas Gallyamov, a former speechwriter for President Putin turned political consultant, said Putin had to step in because, by carrying out the mutiny and remaining free, Prigozhin "shoved Putin's face into the dirt front of the whole world.”

Failing to punish Prigozhin would have offered an “open invitation for all potential rebels and troublemakers,” so Putin had to act, Gallyamov said.

Flight-tracking data reviewed by The Associated Press showed that a private jet previously used by Prigozhin took off from Moscow on Wednesday evening, and its transponder signal disappeared minutes later.

Videos shared by the pro-Wagner Telegram channel Grey Zone showed a plane dropping like a stone from a large cloud of smoke, twisting wildly as it fell, one of its wings apparently missing. A free fall like that typically occurs when an aircraft sustains severe damage, and a frame-by-frame AP analysis of two videos was consistent with some sort of explosion mid-flight.