Kurdish authorities in Iraq said Friday they believe their Peshmerga forces have been attacked with chemical weapons, possibly chlorine gas, by fighters from the Islamic State in Iraq and the Levant (ISIL).

The Kurdistan Region Security Council said it was investigating multiple attacks by ISIL against Peshmerga positions, including in Makhmour, southwest of Erbil, the capital of the autonomous Kurdish region, earlier this week."Initial reporting indicates chemical agents were fired in the form of projectiles, possibly mortar rounds," the council said in a statement. "Several Peshmerga officers were treated for dizziness, vomiting and general weakness, while some are receiving treatment for burns."

It was the third report of suspected chemical weapons use on the Iraqi battlefield this year.

The U.S. Central Command said Thursday that the U.S. and Iraq were investigating reports that ISIL may have used a chemical agent, possibly mustard gas, in an attack in northern Iraq.

Central Command spokesman Col. Pat Ryder said, "We’ve seen those reports. We’re taking them seriously. We’re looking into them, but at this point we really don’t know what — if anything — may have been used."