Turkish forces and their proxies pushed deep into Syria Sunday, moving closer to completing their assault's initial phase, while Washington announced it was pulling out 1,000 troops from the country's north.
The Kurdish administration in northern Syria said that Turkish bombardment near a camp for the displaced led to nearly 800 relatives of ISIS members fleeing.
Fighting raged but Turkish-backed forces made significant progress along the border on the fifth day of an offensive that has provoked an international outcry and left dozens of civilians and fighters dead.
Kurdish authorities and foreign powers have warned repeatedly that the hostilities could undermine the fight against the ISIS group and allow militants to break out of captivity.
Fighting has engulfed the area since Wednesday when Ankara launched a long-threatened offensive against the Kurdish-led Syrian Democratic Forces (SDF), who it considers "terrorists" linked to insurgents inside Turkey.
US Defence Secretary Mark Esper said Sunday that President Donald Trump had ordered the withdrawal of up to 1,000 troops from northern Syria.
"I can't give a timeline because it changes hourly. We want to make sure that we do so in a very safe, deliberate manner," he told the CBS network.
Trump has been accused of abandoning a loyal ally in the fight against ISIS after ordering American troops to pull back from the border, which Ankara took as a green light to move in.
The Syrian Observatory for Human Rights war monitor reported on Sunday that 19 more civilians had been killed in fighting.
More than 50 civilians have now died on the Syrian side, with Turkish reports putting the number of civilians dead from Kurdish shelling inside Turkey at 18.
The Observatory said pro-Ankara fighters "executed" at least nine civilians on Saturday near the Syrian town of Tal Abyad.
The Kurds said a female Kurdish party official and her driver were among those killed.
- Humanitarian fears -
Aid groups have warned of another humanitarian disaster in Syria's eight-year-old war if the offensive is not halted.
The UN humanitarian agency OCHA said the exodus sparked by the fighting had grown to 130,000 people and it was preparing for that figure to more than triple.
"We have moved into a planning scenario where up to 400,000 people could be displaced within and across the affected areas," spokesman Jens Laerke told AFP.
Some 12,000 ISIS fighters -- Syrians, Iraqis as well as foreigners from 54 countries -- are detained in Kurdish prisons, according to official Kurdish statistics.
Displacement camps meanwhile host some 12,000 foreigners -- 8,000 children and 4,000 women.
"The brutal military assault led by Turkey and its mercenaries is now taking place near a camp in Ain Issa, where there are thousands (of people) from families of ISIS," a Kurdish administration statement said.
"Some were able to escape after bombardments that targeted" the camp.
It said the Ain Issa camp was "now without guards" and 785 relatives of ISIS militants had fled.
Save the Children said it was deeply concerned by reports hundreds of women and children linked to ISIS had fled in terror from a camp for displaced people in northern Syria after shells fell on it on Sunday.
Save the Children said the annex of the Ain Issa camp from which they fled had been home to 249 women and 700 children connected to ISIS and warned of “a danger that children of foreign nationals could now be lost in the chaos”.
Reports suggest the annex was now empty of foreign women and “foreign masked men on motorbikes are circling the camp”, Save the Children said in a statement.
The SDF, a coalition of Kurdish and Arab fighters, was the main partner on the ground in the US-led campaign against ISIS.
According to the Observatory, at least 104 of its fighters have been killed since the start of the Turkish offensive.
- Fierce fighting -
According to Turkish media, Ankara aims to take control of a territory 120 kilometers (75 miles) long and 30 kilometers into Syria, up to the towns of Tal Abyad and Ras al-Ain.
Turkish forces and their proxies captured Tal Abyad on Friday afternoon, which left Ras al-Ain, further east, as the last major target in the offensive.
The fighting was intense in and around the town and the Observatory reported that a convoy, which included journalists and civilians, was hit by artillery.
Nine people were killed, five of them civilians, the monitoring organisation said.
Turkey announced it had seized the key M4 highway, which looks like it might mark the southern limit of its advance in this initial phase of the invasion.
It lies 30 to 35 kilometers deep in Syrian territory.
SDF fighters have taken mounting losses against the vastly superior military firepower of Turkey, which has defied mounting international protests and the threat of US sanctions in pressing on with its offensive.