The United Nations has warned that the alleged use of chemical weapons in Iraq's Mosul, if confirmed, would be a war crime and a violation of international humanitarian law.
"This is horrible," said Lise Grande, the humanitarian coordinator in Iraq, in a March 4 statement. "There is never justification -- none whatsoever -- for the use of chemical weapons."
Grande's comment comes one day after reports emerged that chemical weapons have been used in the ongoing battle for Mosul between Iraqi government forces and the Islamic State (IS) extremist group. It was not clear which side was to blame.
The UN's World Health Organization (WHO) said on March 4 that 12 people, including women and children, were being treated for possible exposure to chemical-weapons agents in Mosul.
It said four of them were showing "severe signs associated with exposure to a blister agent." The patients were exposed to the chemical agents in the eastern side of Mosul.
WHO said the patients were being treated in Irbil, the capital of Iraq's Kurdish region, east of Mosul.
The first indication of a potential use of chemical weapons came on March 3, when the International Committee of the Red Cross (ICRC) said seven people -- five children and two women -- had shown symptoms indicative of exposure to a chemical agent.
"If the alleged use of chemical weapons is confirmed, this is a serious violation of international humanitarian law and a war crime, regardless of who the targets or the victims of the attacks are," Grande said.
U.S.-backed Iraqi forces on February 19 began a major offensive to dislodge IS militants from the western section of Mosul, almost a month after they forced militants out of the eastern part of the city.
Most of western Mosul is still under IS control despite recent gains on the city's southwestern edge by Iraqi forces.