Putin delivers mixed tribute to Wagner boss Yevgeny Prigozhin after deadly plane crash

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 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-organized.

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."