Britain, U.S. believe Yevgeny Prigozhin is dead, U.S. disputes missile claim

Meanwhile, the Russian government has denied any involvement in the death of the once Putin ally.

Kremlin spokesperson Dmirty Peskov denied any Russian government involvement.

"There has been a lot of speculation around this crash, the tragic deaths of the plane's passengers, among them Yevgeny Prigozhin. Of course, the West presents all this speculation from a particular angle. All of that is sheer lies," Peskov said.

The British Ministry of Defense said it is "highly likely" that Prigozhin was killed.

"The Russian authorities claim 10 people on board died, including Wagner owner Yevgeny Prigozhin. There is not yet definitive proof that Prigozhin was onboard, and he is known to exercise exceptional security measures. However, it is highly likely that he is indeed dead," the British Ministry of Defense said in an update.

"The demise of Prigozhin would almost certainly have a deeply destabilizing effect on the Wagner Group. His personal attributes of hyper-activity, exceptional audacity, a drive for results and extreme brutality permeated Wagner and are unlikely to be matched by any successor," the Defense Ministry continued.

Pentagon Press Secretary Gen. Pat Ryder said the U.S. believes Prigozhin is dead, but disputed reports of a surface-to-air missile having taken out Prigozhin's jet.

"I'll say right up front, first of all, our initial assessment is that it's likely Prigozhin was killed. We're continuing to assess the situation. We don't have any information to indicate this right now the press reporting stating that there was -- some type of surface-to-air missile that took down the plane that -- we asses that information to be inaccurate," Ryder told a press briefing.

"Again, nothing to indicate -- no information to suggest that there was a surface-to-air missile. But beyond that, I'm really just not going to have any further information," Ryder continued.