A group that monitors the war in Syria said Tuesday it has “confirmed information” about the death of Abu Bakr al-Baghdadi, the leader of the Islamic State, citing information received from the militants in eastern Syria.

Baghdadi’s death has been rumored numerous times in the past, and it was not immediately possible to independently verify the claim. There also were no immediate announcements from the Islamic State’s news channels.

The U.S. Central Command said in a statement, “We cannot confirm this report, but hope it is true.”

“We strongly advise ISIS to implement a strong line of succession. It will be needed,” the statement said, using an acronym for the Islamic State.

The death of Baghdadi — if true — would mark another blow to the extremist group days after it was finally driven from the northern Iraqi city of Mosul by Iraqi-led forces. The militants are also under siege in the Syrian city of Raqqa, the Islamic State’s self-declared capital, where a U.S.-backed force of mainly Kurdish fighters has been advancing for weeks.

[MORE: Iraqi Prime Minister congratulates armed forces for Mosul “victory”]

The monitoring group, the Syrian Observatory for Human Rights, is based in Britain and relies on a network of activists in Syria for its reporting. The group’s director, who goes by the pseudonym Rami Abdulrahman, told The Washington Post that Islamic State leaders had confirmed Baghdadi’s death to the Observatory’s activists in the Syrian province of Deir al-Zour.

“We don’t know when. We don’t know how,” Abdulrahman said.

A post on the Syrian Observatory’s website said it “confirmed information … about the death” of Baghdadi, whose real name is Ibrahim Awad Ibrahim al-Badry.

Baghdadi’s apparent death or capture have been asserted several times over the past decade as his breakaway al-Qaida faction gradually formed into the core of the Islamic State. But the various reports later proved false or could not be substantiated.

Last month, Russia said it was looking into claims that one of its airstrikes in late May outside Raqqa killed Baghdadi. The Russian military later said it could find no clear evidence of Baghdadi’s death. The U.S. military also said at the time it had “no information to corroborate” the Russian reports.

As far back as December 2012, Iraqi officials claimed that they had captured Baghdadi in Baghdad. Iraqi commanders later said the person held was not Baghdadi.

Washington Post writers Brian Murphy and Thomas Gibbons-Neff in Washington contributed to this report.