The US-led coalition has carried out the first air strikes on Islamic State chemical weapons sites, the Pentagon said Thursday, acting on information from a senior operative described as the extremists' top chemical expert.

The successful "multiple" bombings came as a result of detailed intelligence from Sulayman Dawud al-Bakkar, also known as Abu Dawud, Pentagon press secretary Peter Cook said, confirming Dawud's capture by US special forces in Iraq last month.

The snaring of Dawud, who was transferred Thursday into Iraqi custody after interrogation, appears to be a major boon in the fight against the IS group in Iraq and Syria, and Cook said it had yielded almost immediate results as well as critical information for the future.

Cook described Dawud as "ISIL's emir of chemical and traditional weapons manufacturing."

"His capture removed a key ISIL leader from the battlefield and provided the coalition with important information about ISIL's chemical weapons capabilities," Cook said, using an alternative acronym for the IS extremists.

"Through Dawud, the coalition learned details about ISIL's chemical weapon facilities and production, as well as the people involved.

"The information has resulted in multiple coalition air strikes that have disrupted and degraded ISIL's ability to produce chemical weapons and will continue to inform our operations in the future."

US media said that Dawud formerly worked for Saddam Hussein's regime.

The chemical weapons expert was picked up by US forces that the Pentagon only recently deployed to Iraq to conduct raids against the Islamic State group.

The strikes on the chemical facilities -- it was not immediately known exactly where and when the raids took place -- had carefully "factored in" the risk to the civilian population, Cook added.

The New York Times, citing officials, said that the US-led air campaign targeted a weapons production plant in Mosul, Iraq and another against a "tactical unit" near Mosul believed to be linked to the program.

In February, Director of National Intelligence James Clapper and CIA Director John Brennan for the first time openly accused the Islamic State group of using chemical weapons, including mustard gas, in Iraq and Syria.

- 'Gross violations' -

The US military Central Command Thursday provided the most specific details so far of the chemical attacks it attributes to the group.

"We believe that Islamic State for Iraq and the Levant (ISIL) was responsible for the sulfur mustard attack in Marea, Syria on August 21, 2015, largely based on photographic evidence and the Syrian opposition's description of the event," said a CENTCOM statement.

"Based on the available information, we also believe that ISIL was likely responsible for some of the alleged attacks using sulfur mustard in Iraq."

Mustard gas -- also known as "sulfur mustard" -- can cause respiratory distress, momentary blindness and painful blisters.

"Any use by ISIL of CW is a continuation of its extensive record of gross violations of human rights, as well as its blatant disregard for international laws and norms," CENTCOM said.

According to CNN, the US intelligence community has confirmed 12 cases of the use of mustard agent, with three other cases suspected. They include locations in Syria and Iraq.

However, CNN said that US officials have been at pains to play down the attacks saying they believe any deaths were from being hit by artillery, not the agent.

Dawud's capture and the subsequent raids mark the second major blow against the extremists announced this week, in the US-led attempt to wipe out the IS group and its self-declared caliphate across parts of Syria and Iraq where the extremists implement an ultra-conservative interpretation of Islamic law.

Top Islamic State commander leader Omar al-Shishani, known as Omar the Chechen, was badly wounded in a recent US strike in northeastern Syria, though not killed as first believed, according to a monitoring group.

The Britain-based Syrian Observatory for Human Rights said Wednesday that according to its sources the March 4 strike targeted the jihadist's convoy, killing his bodyguards, while Shishani himself "was seriously injured."

A US official had initially said Shishani "likely died" in the assault by waves of US warplanes and drones -- but the United States had stopped short of announcing his death, which had been erroneously reported several times before.

The US official branded Shishani "the ISIL equivalent of the secretary of defense."

Shishani was one of the IS leaders most wanted by Washington, which put a $5 million bounty on his head.