Thousands of people have fled the Mosul area and more are expected as Iraqi troops move on the city to liberate it from the so-called Islamic State (IS).
Some 5,000 people have crossed the border into Syria in the last 10 days, about 900 of them since the military began in areas around Mosul on Monday.
They have arrived at the al-Hol refugee camp where conditions, aid workers say, are already filthy and overcrowded.
Up to 1.5 million are thought to be in Mosul, with up to 5,000 IS fighters.