The Islamic State (also known as ISIS) has been accused of carrying out a chemical attack in Mosul last week, which, if confirmed, would appear to be the first time it has used this tactic during its battle with Iraqi government forces to retake control of the city.

The International Committee of the Red Cross (ICRC) said in a statement that about twelve people, including women and children, were being treated for possible exposure to chemical weapons in a hospital in Erbil. While the ICRC stressed tests had not yet proved conclusive, it found the symptoms of the hospitalized patients suggested that they had been exposed to mustard agent. Iraqi authorities have said that ISIS was behind the attack.

Displaced Iraqis flee their homes as Iraqi forces battle with Islamic State militants, in western Mosul, Iraq March 6, 2017.

© 2017 Reuters

The use of chemicals as a weapon is a war crime. It is also a serious threat to both civilians and combatants, particularly in a city as densely populated as Mosul.

Yet this latest reported chemical attack would not be ISIS’s first in Iraq. After Iraqi troops retook the town of Qayyarah, 60 kilometers south of Mosul last year, ISIS launched at least three chemical attacks in September and October.

The attacks caused painful burns to at least seven people that were consistent with exposure to a mustard agent also known as a “vesicant,” or blister agent, a chemical weapons expert told Human Rights Watch. In two other cases in March 2016, first responders told Human Rights Watch they witnessed at least two other chemical attacks targeting the Kurdistan Regional Government’s Peshmerga military forces in Taza Khurmatu, a town 100 kilometers south of Erbil. The perpetrators of those attacks have not been confirmed but witnesses believed them to be ISIS.

Despite reports of US-led coalition airstrikes targeting ISIS’ chemical weapons production facilities in Iraq, this new attack serves as a troubling reminder that ISIS still has chemical warfare capabilities – even as it loses ground in western Mosul.

In light of these attacks, both Iraqi authorities and other states and organizations assisting in humanitarian protection should urgently deploy defensive measures to safeguard civilians, including stockpiling masks and other protective equipment that can be rapidly distributed to civilians.

They should also inform civilians on what to do in case they find themselves in an area under chemical weapons attack, and restrict access to contaminated areas.