Moscow, Russia - Russian President Vladimir Putin on Thursday expressed his "condolences" over a plane crash that killed Wagner chief Yevgeny Prigozhin, describing him as a man who made mistakes but "achieved results".

An investigation is currently underway into what caused Wednesday's crash, which came exactly two months after Wagner's short-lived rebellion against Moscow's military leadership.

"First of all, I want to express words of sincere condolences to the families of all the victims," Putin said in a televised meeting, calling the incident a "tragedy."

"I knew Prigozhin for a very long time, since the early 90s. He was a man of complicated fate, and he made serious mistakes in his life, but he achieved the right results," Putin added.

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He said that an investigation had been launched into the crash and that "it will take some time."

"It will be conducted in full and brought to a conclusion. There is no doubt about that," Putin said, in footage showing a meeting with the Russian-installed head of the Donetsk region Denis Pushilin.

The circumstances of the crash, which claimed the lives of some of Prigozhin's close entourage, have prompted furious speculation about a possible assassination.