MOSCOW: Russian President Vladimir Putin sent his condolences to the family of Yevgeny Prigozhin on Thursday, breaking his silence after the mercenary leader's plane crashed with no survivors two months after he led a mutiny against army chiefs.

Putin's comments, which suggested he harboured decidedly mixed feelings about Wagner's mercenary boss, were the most definitive yet on Prigozhin's fate. Before he spoke, the only official statement had come from the aviation authority which said Prigozhin had been on board the downed plane.

Russian investigators have opened a probe into what happened, but have not yet said what they suspect caused the plane to suddenly fall from the sky northwest of Moscow on Wednesday evening.

Nor have they officially confirmed the identities of the 10 bodies recovered from the wreckage.

U.S. officials told Reuters that Washington is looking at a number of theories over what brought down the plane, including a surface-to-air missile.

The U.S. Department of Defense on Thursday said there was currently no information to suggest that a surface-to-air missile took down the plane.

The presumed death of Prigozhin leaves Russian President Vladimir Putin stronger in the short term, removing a powerful figure who launched a June 23-24 mutiny against the army's leadership and threatened to make him look weak.

But it would also deprive Putin of a forceful and astute player who had proved his utility to the Kremlin by sending his fighters into some of the bloodiest battles of the Ukraine war and by advancing Russian interests across Africa which are now likely to be re-organised.

It remains to be seen too how Wagner fighters, some of whom have already spoken of betrayal and foul play, react.

Pledging a thorough investigation which he said would take time, Putin said that "preliminary data" indicated that Prigozhin and other Wagner employees had been on the downed plane. The passenger list suggests that Wagner's core leadership team were flying with him too and had also perished.

Putin paid generous tribute to the renegade mercenary calling him a talented businessman who knew how to look after his own interests and who could, when asked, do his bit for the common cause.

But he also described Prigozhin as a flawed character who had made some bad mistakes.

"I want to express my most sincere condolences to the families of all the victims. It's always a tragedy," Putin said in televised remarks made during a meeting in the Kremlin with the Moscow-installed chief of Donetsk region in eastern Ukraine.

"I had known Prigozhin for a very long time, since the start of the 90s. He was a man with a difficult fate, and he made serious mistakes in life."

Chechen leader Ramzan Kadyrov, one of Putin's most loyal allies, said that Prigozhin was his friend and he had asked the mercenary chief "to set aside his personal ambitions".

"But lately he either did not see or did not want to see a full picture of what was going on in the country," Kadyrov said.

'A METALLIC BANG'

The Embraer Legacy 600 EMBR3.SA executive jet, which had been flying from Moscow to St. Petersburg, crashed near the village of Kuzhenkino in the Tver region north of Moscow.

A Reuters reporter at the crash site on Thursday morning saw men carrying away black body bags on stretchers. Part of the plane's tail and other fragments lay on the ground near a wooded area where forensic investigators had erected a tent.

The Baza news outlet, which has good sources among law enforcement agencies, reported that investigators were focusing on a theory that one or two bombs may have been planted on board.

Residents of Kuzhenkino, the village near the crash site, said they had heard a bang and then saw the jet plummet to the ground. The plane showed no sign of a problem until a precipitous drop in its final 30 seconds, according to flight-tracking data.

One villager, who gave his name as Anatoly, said: "It wasn't thunder, it was a metallic bang - let's put it that way."

Mourners left flowers and lit candles near Wagner's offices in St. Petersburg and at other locations across Russia.

A Telegram channel linked to Wagner, Grey Zone, pronounced Prigozhin dead on Wednesday evening, hailing him as a hero and a patriot who had died at the hands of "traitors to Russia".

Russian militants who fight on Ukraine's side and have carried out several attacks on Russian border regions urged the Wagner Group to avenge Prigozhin's death and join their ranks. It was not immediately clear how members of the Wagner Group reacted to their call.

Amid the absence of verified facts, some of his supporters have pointed the finger of blame at the state, others at Ukraine, which marked its Independence Day on Thursday

Putin said in June that Prigozhin's the mutiny against the army, which saw Wagner fighters shoot down Russian military helicopters, could have tipped Russia into civil war.

The mercenary leader had also spent months criticising the conduct of Russia's war in Ukraine - which Moscow calls a "special military operation" - and had tried to topple Defence Minister Sergei Shoigu and Valery Gerasimov, chief of the General Staff.

The mutiny was ended by an apparent Kremlin deal which saw Prigozhin agree to relocate to neighbouring Belarus. But he had appeared to move freely inside Russia.

Many Russians had wondered how he was able to get away with such brazen criticism without consequence.

Prigozhin posted a video address on Monday which he suggested was made in Africa. He turned up at a Russia-Africa summit in St. Petersburg in July.