US airstrikes in Iraq
Smoke rises during clashes between Kurdish Peshmerga fighters and Islamic State (IS) militants on the outskirts of MosulReuters

An airstrike in northern Iraq has killed a chemical weapons expert operating for Islamic State (Isis), US officials said.

Authorities believe Abu Malik's death is likely to be a significant setback for the Sunni insurgents, who captured vast swathes of territory in Iraq and Syria.

The Pentagon said in a statement: "His past training and experience provided the terrorist group with expertise to pursue a chemical weapons capability."

"His death is expected to temporarily degrade and disrupt the terrorist network and diminish (IS') ability to potentially produce and use chemical weapons against innocent people."

Though there have been unverified reports suggesting the dreaded Iraqi militant group has kept its hands on chemical weapons, there is no credible information to substantiate the claim. But officials have confirmed IS intends to get ready for using chemical weapons.

Malik, a chemical weapons engineer, who worked under former dictator Saddam Hussein, joined the al-Qaeda group before switching his allegiance to the IS. He is believed to have worked at Iraq's notorious Muthanna chemical weapons facility until 2005. It is unclear how long Malik spent time at the facility.

The US-led coalition has been conducting airstrikes in Iraq and Syria against IS positions ever since the militants' advance began to spiral out of control. More than 2,000 aerial raids have been launched so far at an estimated cost of about $1.3bn.