BBC report that, Russia's defence ministry is investigating whether one of its air strikes in Syria killed the leader of the Islamic State militant group (IS).
The ministry said an air strike may have killed Abu Bakr al-Baghdadi and up to 330 other fighters on 28 May.
It said the raid had targeted a meeting of the IS military council in the group's de-facto capital of Raqqa, in northern Syria.
There have been a number of previous reports of Baghdadi's death.
This is the first time, after all , that Russia has said it may have killed the IS leader.
Meanwhile, other media reports have previously claimed he had been killed or critically injured by US-led coalition air strikes.
Nonetheless, Colonel John Dorrian, a spokesman for the US-led coalition, said the US could not confirm whether Baghdadi had been killed.
There has been no official comment from Syria's government.