BAGHDAD (AP) — The United Nations says nearly half a million civilians have fled Mosul since U.S.-backed Iraqi forces launched a wide-scale military operation last October to retake the city from Islamic State militants.

The U.N. Office for the Coordination of Humanitarian Affairs said Monday that 493,000 people have been displaced from the city. As many as 500,000 others are in IS-controlled parts of western Mosul, where fighting is still underway.

The U.N. says food, water and medicine stocks are running low in the western half of the city, and that the fighting there is much heavier than it was in eastern Mosul, which the Iraqi government declared "fully liberated" in January.