Russia's defence ministry said a week ago it believed it may have killed Baghdadi when one of its air strikes hit a gathering of senior ISIS commanders on the outskirts of the Syrian city of Raqqa.
But armed groups fighting in the region and US officials say they have no evidence that Baghdadi was killed, and many regional officials have said they are sceptical about the information from Moscow.
Committee head Viktor Ozerov was quoted as saying the defence ministry would not have released information about Baghdadi's death if it believed it could be later proved incorrect.
"I think this information is close to 100 percent," Interfax quoted Ozerov as saying. "The fact that ISIS has still not shown him anywhere also adds to our confidence that al-Baghdadi has been killed."
Baghdadi has frequently been reported killed or wounded since he declared a caliphate from a mosque in Mosul in 2014, after leading his fighters on a sweep through northern Iraq.
His death would be one of the biggest blows yet to the terrorist group, which is trying to defend its shrinking territory in Syria and Iraq against forces backed by regional and global powers.