Russia is trying to verify reports that its military has killed the leader of the Islamic State group in an air strike targeting a meeting of militant leaders.
The Defence Ministry claimed that Abu Bakr al-Baghdadi was killed in late May with other senior group commanders just outside the group's de facto capital in Syria, adding that information is "being verified through various channels".
Foreign minister Sergey Lavrov said: "I don't have a 100% confirmation of the information."
If confirmed, it would mark a major military success for Russia, which has conducted a military campaign in support of Syrian president Bashar Assad since September 2015.
A spokesman for the US-led anti-IS coalition said he could not confirm the Russian claim.
Earlier, the ministry said the air raid on May 28 also killed about 30 mid-level militant leaders and about 300 other fighters.
It added the strike came as IS leaders gathered to discuss the group's withdrawal from Raqqa.
Russia says the military began planning the hit after getting word that the IS leaders were going to gather for a meeting to plan their exit to the south.
The Russian military sent drones to monitor the area and then dispatched a group of Su-34 bombers and Su-35 fighter jets to hit the IS gathering. It said in a statement:
"According to the information that is being verified through various channels, IS leader Abu Bakr al-Baghdadi also attended the meeting and was killed in the airstrike."
The ministry added that it had warned the US of the coming strike.
It said other militant leaders killed in the raid included IS leaders Abu al-Khadji al-Mysri, Ibrahim al-Naef al-Khadj and Suleiman al-Shauah.
The report of al-Baghdadi's death comes as IS suffers major setbacks in which they have lost wide areas of territory and both of their strongholds - Mosul, Iraq and Raqqa, Syria.
Both are still under attack by various groups fighting under the cover of air strikes by the US-led coalition.