The Russia Defense Ministry announced on Friday that they are investigating reports that Abu Bakr al-Baghdadi, the head of the Islamic State (ISIS), was killed in an airstrike on May 28.

The Russians claim he was killed in an airstrike that hit on the outskirts of Raqqa, a city that is being used as the terror groups capitol. Russian media reported over that the strike killed killed around 30 mid-level Isis leaders and another 300 fighters. Russia said multiple Su-24 and Su-25 aircraft were involved in the strike, acting upon advance intelligence provided by drone footage. The Russian military said it had informed the US in advance of the strike.

“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 in a statement.

In March, US Secretary of State Rex Tillerson said that “nearly all” of Baghdadi’s deputies had been killed.

“It is only a matter of time before Baghdadi himself meets this same fate,” he added.

US officials announced they could not confirm the Russian claim. Baghdadi has been reported killed in the past several times, but those reports turned out to be inaccurate.