WASHINGTON: U.S.-led coalition warplanes destroyed a factory in Iraq used by ISIS to make chemical weapons, the Pentagon said said Tuesday.

The production center – a converted pharmaceutical plant complex – likely made chlorine or mustard gas, said Lieutenant General Jeffrey Harrigian, who heads U.S. Air Forces Central Command.

"This represents just another example of Daesh blatant disregard for international law and norms," he told Pentagon reporters in a video call, using an Arabic acronym for ISIS.

The strike occurred Monday near Mosul and was conducted by fighter jets, ground-attack craft and even a B-52 heavy bomber, the Pentagon said.

Observers have repeatedly alleged ISIS has used chemical weapons, and the Pentagon has confirmed the extremists have deployed chlorine and sulfur mustard devices.

Iraqi security forces, backed by coalition air power, are in the final weeks of "shaping" operations ahead of an assault to recapture Mosul, which ISIS seized in 2014 and which remains the extremists' last main stronghold in Iraq.