Yevgeny Prigozhin, the director of Wagner, was one of the ten people on board a jet that crashed in Russia, killing all ten people on board.
He was thought to be travelling on the aircraft.
Earlier, the air defences in the Tver region, north of Moscow, shot down the jet, according to a Telegram account with ties to Wagner called Grey Zone.
In June, Prigozhin was the leader of a failed uprising against the Russian military.