A purported statement by the Islamic State group claims that an American female hostage has been killed in Jordanian airstrikes on the outskirts of the northern Syrian city of Raqqa, the group's main stronghold.

It identified the woman as Kayla Jean Mueller and said she was killed Friday during Muslim prayers in airstrikes that targeted "the same location for more than an hour."

It published photos allegedly of the bombed site, showing a damaged three-story building.

American officials said they were looking into the report. The White House said it did not have immediate comment.

The statement could not be independently verified. It appeared on a militant website commonly used by IS.

Mueller is an aid worker whose identity was never disclosed out of concerns for her safety.