Ukraine's Zelenskiy says Putin killed mercenary boss Prigozhin

Ukraine's President Volodymyr Zelenskiy during a press conference with Denmark's Prime Minister Mette Frederiksen

KYIV (Reuters) -Ukrainian President Volodymyr Zelenskiy said on Friday Russian leader Vladimir Putin was behind the death of mutinous mercenary boss Yevgeny Prigozhin, who died in an unexplained plane crash with his top lieutenants last month.

Zelenskiy, who provided no evidence to back up his assertion, made the comment in passing at a conference in Kyiv as he was asked a question about the Russian president.

"The fact that he killed Prigozhin - at least that's the information we all have, not any other kind - that also speaks to his rationality, and about the fact that he is weak," Zelenskiy said.

The Kremlin says all possible causes of the crash will be investigated, including the possibility of foul play. It has called the suggestion that Putin ordered the deaths of Prigozhin and his men an "absolute lie".

Prigozhin this summer led a brief mutiny in Russia that posed the biggest challenge to Putin's rule since he rose to power in 1999. It prompted the Kremlin chief to accuse its authors of "treason" and a "stab in the back".

Many critics of Putin have died in unclear circumstances during his 23 years in power, or narrowly escaped dying.

(Reporting by Dan Peleschuk; writing by Tom Balmforth; editing by Timothy Heritage)