The international coalition battling the “Islamic State of Iraq and Syria” (ISIS) said Friday (June 16th) it could not confirm the death of the group’s leader, following Russia's claim that he might have been killed, AFP reported.

"We cannot confirm these reports at this time," said coalition spokesman Col. Ryan S. Dillon.

The Russian army said earlier that it hit ISIS leaders in an airstrike in Syria last month and was seeking to verify whether ISIS chief Abu Bakr al-Baghdadi had been killed.

It said it had informed Washington of the May 28th strike near the group’s Syria stronghold of al-Raqa, which is now under assault by the Syrian Democratic Forces (SDF).

"Senior commanders of the military groups of the so-called ISIS military council, 30 mid-ranking field commanders and up to 300 militants who provided security for them were eliminated," it said.

"According to information which is being checked through various channels, the leader of ISIS Ibrahim Abu Bakr al-Baghdadi was also present at the meeting and was eliminated by the strike."

The elusive, Iraqi-born ISIS leader has not been seen in public since proclaiming himself "caliph" in the Iraqi city of Mosul three years ago.

The world's most-wanted man has been rumoured wounded or killed a number of times in the past.

He has been nicknamed "The Ghost" as he has been reportedly spotted around the Syrian-Iraqi border, but his whereabouts have never been confirmed.