Wagner boss Yevgeny Prigozhin was on the passenger list of a plane which crashed in Russia, killing all 10 on board.
He was believed to be on board the plane.
Earlier, a Wagner-linked Telegram channel Grey Zone reported that the jet was shot down by air defences in Tver region, north of Moscow.
Prigozhin led a failed mutiny against the Russian armed forces in June.
Prigozhin is the head of the Wagner mercenary group, which he established in 2014.
A wealthy businessman with a criminal record, he was known as “Putin’s chef” because he provided catering for the Kremlin.
In June he led his troops on a short-lived mutiny, after they seized control of the southern Russian city of Rostov-on-Don and moved towards Moscow, with the stated aim of removing the military leadership.
However, Prigozhin stopped the advance after negotiations with the Kremlin, which were mediated by Belarusian leader Alexander Lukashenko.
Under a deal to end the mutiny, charges against Mr Prigozhin were dropped and he was offered a move to Belarus.
He has kept a low profile since then, although a video released a few days ago suggested he was in an African country.
