Abu Bakr al-Baghdadi
Abu Bakr al-BaghdadiReuters

Russia's Foreign Ministry said Thursday that it is "highly likely" that Islamic State (ISIS) leader Abu Bakr Al-Baghdadi was killed in Russian airstrikes last month.

"According to the Russian Defense Ministry, it is highly likely that Daesh leader Al-Baghdadi was eliminated as a result of a Russian Aerospace Forces strike on the terrorists' command post in the southern suburb of the city of Raqqa in late May this year," Deputy Foreign Minister Oleg Syromolotov told the Sputnik news agency, using the Arabic acronym for ISIS.

He stressed that the "information is now verified through various channels."

Last week, the Russian Defense Ministry said that Al-Baghdadi might have been among a group of ISIS members who were killed in a Russian air strike on May 28 south of Raqqa, ISIS's de facto capital in Syria.

Russian Foreign Minister Sergey Lavrov, commenting on the news, said he could not give firm proof that the ISIS leader was indeed killed. The Pentagon expressed skepticism over the claim as well.

There have been many reports in recent years that Al-Baghdadi was injured or killed, but none of them have been confirmed.

Late last year, he refuted those reports by releasing an audio message in which he said he is "confident of victory" and called on the people of Mosul to fight the "enemies of God".