BAGHDAD — An Iraqi military officer says Islamic State militants have launched a gas attack in a newly-liberated area in western Mosul.

The officer with the anti-terrorism forces said Saturday that the attack occurred the night before in the al-Abar neighborhood, when IS fired a rocked loaded with chlorine. He said seven soldiers suffered breathing problems and were treated in a nearby field clinic.

The officer spoke on condition of anonymity as he was not authorized to release information.

U.S.-backed Iraqi forces are currently battling IS militants in the more densely-populated western half of Mosul. Iraqi officials say more than half of western Mosul has been retaken. The extremists were driven out of the eastern half of Mosul, Iraq’s second-largest city, in January.