Chechen rebel leader Doku Umarov, who claimed the Moscow Metro bombings earlier this year which killed 40 people, is said to be resigning.
In a video released online a man appearing to be Mr Umarov, 46, says he is handing over to a younger comrade.
The speaker says a man seated next to him, named as Aslambek Vadalov, can lead “more energetically”.
Doku Umarov is one of the few rebel leaders to survive from Chechnya’s spell of independence from Russia.