Islamic State forces (Isis) have used chemical weapons against Iraqi government forces at least three times between September and October, creating a serious threat to civilians and combatants in and around the embattled city of Mosul.

The attacks hit the town of Qayyarah, 60 kilometers south of Mosul, in September and October after Iraqi government forces retook the town on August 25, 2016. The attacks caused painful burns to at least seven people consistent with exposure to low levels of a chemical warfare agent known as “vesicants,” or blister agents, a chemical weapons expert told Human Rights Watch.

"Isis attacks using toxic chemicals show a brutal disregard for human life and the laws of war,” said Lama Fakih, deputy Middle East director at Human Rights Watch.

The agent used is suspected to be Sulfur mustard, a common type of blister agent, after reports of “garlic” odor and the burning of the eyes, followed by the subsequent reddening of the skin and the delayed appearance of blisters.

A more definitive identification of chemicals used in these attacks would require the analyses of soil and water samples collected by specialized teams near the attack sites and of tissue samples collected from the victims, the Human Rights Watch reported.

Isis had previously used blister agents, including in an attack on areas held by armed opposition groups in Syria in August 2015, according to a United Nations-appointed investigative committee.

"Isis has sought to paint itself as protector of Sunni Arabs in Iraq, yet it is willing to use chemical weapons on them in their own homes,” Fakih said.