(MENAFN) Islamic State (IS) militants are using small commercially purchased drones to attack Iraqi security forces in the battle for Mosul, a US commander said on Wednesday.

Colonel Brett Sylvia, who commands an "advise and assist" US unit in Iraq, said IS militants are attaching small munitions to quadcopters in an attempt to kill local forces as they are retaking Mosul, the last major IS bastion in Iraq.

"They are small drones with small munitions that they've been dropping," Sylvia said.

While the munitions were no larger than "a small little grenade," he said, that was enough to do what "Daesh does, and that's just, you know, indiscriminate killing," he said, using an Arabic acronym for IS.