Did ISIS use chemical weapons to target Kurds in Iraq?

Fragments from mortars fired by Islamic State militants at Kurdish fighters in northern Iraq earlier this month tested positive in a US military field test for the chemical weapons agent sulfur mustard, a US general said on Friday.

Marine Corps Brigadier General Kevin Killea, chief of staff for operations against the militant group, said the field test was not conclusive proof of chemical weapons use, and the fragments are undergoing more definitive testing to confirm the finding.

Killea said the mortar shells had been fired at Kurdish Peshmerga positions near the town of Makhmur in north-central Iraq on August 11. Fragments of the shells were collected by the Kurdish fighters and handed over to US forces in the region.

"We were able to take the fragments from some of those mortar rounds and do a field test...on those fragments, and they showed the presence of HD, or what is known as sulfur mustard," Killea said.

He said sulfur mustard is a Class 1 chemical agent, which means it has few uses outside chemical warfare. "It is very important to understand here that that is a presumptive field test and it is not conclusive, and what those results tell us is merely the presence of that chemical," Killea said.

Killea said that it would take a couple of weeks to get more information on the fragments and that testing is under way.