June 16 (UPI) — The Russian Defense Ministry said Friday it is investigating whether a Russian airstrike killed the Islamic State’s top leader.

A May 28 airstrike on a suburban Raqqa, Syria, command post killed as up to 30 leaders and 300 troops in the militant group also identified as Daesh, ISIS and ISIL. Reclusive leader Abu Bakr al- Baghdadi was present “and was eliminated in the strike,” the ministry said. It added that the information “is being verified via different channels.”

Reports of al-Baghdadi’s death regularly surface, but the statement Friday was the first time Russia acknowledged that it may have killed him. The ministry added that among those killed in the attack by Su-35 and Su-34 fighter planes were Abu al-Hadji al-Mysri, Raqqa emir; Emir Ibrahim al-Naef al-Hadj, leader of territory between Raqqa and Es-Suhne; and IS security chief Suleiman al-Shauah.

Al-Baghdadi was believed to be in Mosul, Iraq, prior to a U.S.-led coalition effort in October 2016 to take the city. The coalition has not reported his whereabouts since; his only known public appearance was a sermon in a Mosul mosque in July 2014. Since then, IS lost control of territory in Syria and Iraq and has been the constant target of Russian and coalition airstrikes.

In March, U.S. Secretary of Rex Tillerson said that nearly all of al-Baghdadi’s subordinates have been killed.

“It’s only a matter of time before Baghdadi himself meets the same fate,” Tillerson said.