Moscow - The Russian army on Friday said it hit Islamic State leaders in an airstrike in Syria last month and was seeking to verify whether ISIS chief Abu Bakr al-Baghdadi had been killed.In a statement, the army said Sukhoi warplanes carried out a 10-minute night-time strike early on May 28 at a location near Raqa, where ISIS leaders had gathered to plan a pullout by militants from the group's stronghold."Senior commanders of the military groups of the so-called IS military council, 30 mid-ranking field commanders and up to 300 militants who provided security for them were eliminated," it said."According to information which is being checked through various channels, the leader of ISIS Ibrahim Abu-Bakr al-Baghdadi was also present at the meeting and was eliminated by the strike," it said.ISIL is an acronym for the so-called IS group, also known as ISIS and Daesh.The strike occurred from 21:35 to 22:45 GMT on May 27 following confirmation of the meeting by a drone. Those killed included the emir of Raqa and the IS security chief, the statement said.The US has been informed about the attack, the statement added.Elusive ISIS supremo Baghdadi has not been seen in public since proclaiming himself "caliph" in the Iraqi city of Mosul three years ago.His group has earned global notoriety for imposing a hardline form of Islam that has included stonings, beheadings and amputations.'Matter of time' The Iraqi-born world's most-wanted man has been rumoured wounded or killed a number of times in the past.He has been nicknamed "The Ghost" as he has been reportedly spotted around the Syrian-Iraqi border but his whereabouts have never been confirmed.In March, US Secretary of State Rex Tillerson declared that Baghdadi's death is imminent since "nearly all" of his deputies are dead and "it is only a matter of time" before the IS chief himself meets the same fate.Russia in September 2015 launched a bombing campaign in Syria in support of Syrian President Bashar al-Assad and its efforts against IS jihadists are separate from the US-led coalition which supports Syrian rebels.The Russian military said earlier this month that its planes also struck ISIS convoys attempting to leave Raqa from the south toward Palmyra on May 29, killing 80 militants.Moscow also struck on May 31 ISIS contingents which had left Raqa and were located near Palmyra by firing guided missiles from warships deployed off the Syrian coast.Meanwhile, US-backed Syrian Democratic Forces have been pushing into Raqa from the north, last Tuesday breaking into the ISIS bastion for the first time since it became a hub of the group's self-declared caliphate and the scene of its most gruesome atrocities.Iraqi forces are meanwhile battling IS in the group's second hub Mosul, where the jihadists are confined to just a few neighbourhoods in the west of the city.The Raqa advance caused alarm this week at the United Nations, whose investigators said civilian loss of life was "staggering" due to "excessive" air strikes.