"According to information which is verified through various channels, the meeting was also attended by the leader of ISIS, Ibrahim Abu Bakr al-Baghdadi, who was also killed during the airstrike", the defense ministry says.
Representatives of the United States' Army had also reported about the death of the IS group's leader, but later the report was either denied or al-Baghdadi released video messages with calls for his supporters.
Russian Federation says it may have killed the head of ISIS Ibrahim Abu-Bakr al-Baghdadi and the leadership of the terrorist organisation.
A statement issued today from the ministry said the bombing raid had targeted the meeting on May 28 and among those "liquidated" were reported to be al-Baghdadi, 30 of his leaders and 300 fighters.
The death of one of the world's most-wanted jihadist leaders would be a military victory for Russian Federation and a setback for the militants, who are battling for control of strongholds in Iraq and Syria, including their de facto capital in Raqqah. "If al-Baghdadi is dead-that's good; if not, Russian Federation still demonstrated that it is fighting against the ISIL and trying to make progress", Kozhanov adds, using another acronym for ISIS.
The agency says that under al-Baghdadi, IS has been responsible for thousands of deaths in the Middle East, including American citizens, and terrorist attacks elsewhere.
Another Iraqi intelligence official said the Russians had not shared any information with Iraqi authorities to indicate Baghdadi was killed.
The Russians further claimed they had information indicating the meeting was a leadership gathering to discuss withdrawing from Raqqa, the group's self-proclaimed capital in Syria.
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Baghdadi has not been seen in public since proclaiming himself "caliph" in the Iraqi city of Mosul three years ago.
There have previously been unconfirmed reports, including in March 2015 and in June 2016, that al-Baghdadi was seriously wounded in airstrikes carried out by US -led coalition forces.
Al Qaeda leaders later severed relations with him, saying he was insubordinate, killing too many civilians.
It also claimed the June 3 London attack that killed eight people.
She added that "al-Baghdadi has been reported to have been at least killed or wounded in the past, and in none of those instances has that been confirmed". The group is under assault in its strongholds in both Iraq and Syria, with its presence in Mosul, Iraq near collapse.
CBS News scanned reports from activist and opposition groups with contacts on the ground in the region and found only one - by the usually-reliable Syrian Observatory for Human Rights (SOHR) - about strikes by USA -led coalition warplanes targeting an ISIS convoy, including senior leaders, on May 25, in the southern Raqqa countryside. The US offered a reward of $25 million for his capture or death in 2011.
Abu Bakr al-Baghdadi, which is a nom de guerre, was born Ibrahim Awwad Ibrahim Ali al-Badri al Samarrai.
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