US forces have no reason to think Islamic State leader Abu Bakr al-Baghdadi was wounded in an air strike against an Iraqi target last month, the Pentagon said Tuesday.

British daily The Guardian had earlier reported that the militant, who styles himself caliph of the jihadists' territory in Iraq and Syria, had been "seriously wounded" in an allied raid.

But Pentagon spokesman Colonel Steve Warren told reporters the report appears to have been "recycled" from a March story and that Baghdadi had not been a target of the raid in question.

"We said that there was nothing to indicate that Baghdadi had been wounded or killed," Warren said. "There's nothing to indicate that there's been a change."

US and allied Western and Arab forces are engaged in an air campaign against Baghdadi's so-called Islamic State, a jihadist group that has seized cities in Syria and northern Iraq.

US and Iranian-backed Iraqi forces and Shiite militias have made some progress in recent weeks against the Sunni militants, but the group has itself launched an offensive in western Iraq.