BAGHDAD (AP) — The Islamic State group has been shooting at civilians as they try to flee the nearly two-week battle between Iraqi government forces and IS militants in the city of Fallujah, west of Baghdad, an international aid organization and Iraqi military say.

On Sunday, the militants shot and killed seven civilians and seven IS defectors inside Fallujah as they attempted to flee, Iraqi Maj. Ali Hanoon said.

Hanoon, who is with the elite Iraqi counterterrorism forces, on Monday put the number of civilians killed by IS since the operation started at “dozens” but declined to be more specific, saying the information coming out of Fallujah is sporadic and often incomplete. Iraqi officials say the total is likely higher.

Iraqi forces, backed by U.S.-led coalition airstrikes, have been fighting to retake the IS-held city of Fallujah since late May, but the advance stalled last week because of heavy resistance the militants have put up and because an estimated 50,000 civilians remain trapped inside the city.