MOSCOW (AP) — A senior Russian diplomat says the head of the Islamic State group has most likely been killed in a Russian airstrike.

Deputy Foreign Minister Oleg Syromolotov told the state-run RIA Novosti news agency Thursday that "according to the Defense Ministry's information, there is a high probability that (Abu Bakr) al-Baghdadi has been killed when the Russian air force hit militants' headquarters on the southern outskirts of Raqqa in late May." He wouldn't offer details.

The Defense Ministry first made the claim Friday, adding that al-Baghdadi's death in the May 28 strike was still "being verified through various channels." Syromolotov similarly said that the checks were continuing.

He added that al-Baghdadi's demise would mark a "major success in the fight against international terrorism," spreading "fear and panic" in the IS ranks.