A US-led coalition air strike has killed a former Saddam Hussein chemical weapons specialist with the Islamic State group in Iraq.

US military officials say the air raid carried out last Saturday near Mosul took out Abu Malik, whose training "provided the terrorist group with expertise to pursue a chemical weapons capability", the military said in a statement.

Malik had worked at a chemical weapons production plant under Saddam's regime and later forged an affiliation with Al-Qaeda in Iraq in 2005, before joining the extremist IS group, according to Central Command.

"His death is expected to temporarily degrade and disrupt the terrorist network and diminish ISIL's ability to potentially produce and use chemical weapons against innocent people," it said.

There has been no sign that the IS group possesses a major chemical weapons arsenal. But there have been allegations the jihadists have employed chlorine gas, which is classified as a "choking agent", though not as lethal as nerve agents.

The US-led coalition has carried out more than 2000 air raids against the IS group in Syria and Iraq since August 8, including some bombing runs that targeted senior militants.