Russia's Defense Ministry says it is investigating reports that ISIS leader Abu Bakr al-Baghdadi was killed in one of its airstrikes in Syria last month.
The airstrike on May 28 was carried out on the outskirts of the militant group's de facto capital Raqqa, on a command post where ISIS leaders were meeting, according to Russian state media reports.
"According to information, which is being verified via different channels, the meeting was also attended by the (ISIS) leader Ibrahim Abu Bakr al-Baghdadi, who was eliminated in the strike," the ministry said, according to the TASS report in English. Other state media reported that more than 300 "terrorists" were killed in the strike.
The leaders were discussing their exit from the city through the so-called southern corridor, the ministry said.
The airstrike was carried out following drone footage confirmation of the council's meeting location, state-run Sputnik reports.
Col. Ryan Dillon, a spokesman for the US-led coalition's operation against ISIS in Syria and Iraq, said he "cannot confirm these reports at this time."
US defense officials say they are aware of reports of the strike and is looking for information to confirm it.
CNN is not able to verify the Russian claims, and there have been multiple reports of Baghdadi's death in the past that have turned out to be false.
Al-Baghdadi: An elusive and brutal leader
Officials had long described the ISIS leader as enemy No. 1 in the fight against ISIS, and speculation had swirled over his whereabouts.
Baghdadi has kept a low profile, speaking out in occasional videos and audio messages.
He gave a sermon at a mosque in the Iraqi city of Mosul in 2014, in which he declared himself the leader of his envisaged Islamic caliphate. The sermon was filmed and widely watched around the world.
US forces captured him in Falluja, Iraq, in 2004. At the time, he was considered a low-level al Qaeda member.
He was freed in 2009, and within a year was the leader of Iraq's al Qaeda affiliate, heading up a renewed campaign of bombings and assassinations. Al Qaeda leaders later severed relations with him, saying he was insubordinate, killing too many civilians.
As the leader of ISIS, which has seized and lost swaths of territory in Iraq and Syria, he earned a reputation for brutality.
The extremist group brought a reign of terror and intimidation into areas where they gained control. And the brutality has continued, despite military setbacks. In one reported case, ISIS slaughtered 163 civilians and left their bodies in the street for days, the United Nations said.
US authorities offered a $25 million reward for information leading to his capture.