An elderly man is evacuated from a building in Akcakale, a town near the Turkish border with Syria on Sunday, after it was hit by a rocket reported to be fired from within Syria. Photo: AFP

Hundreds of relatives of foreign jihadists escaped from a displacement camp in northern Syria, Kurdish authorities said Sunday, as the number of people fleeing a Turkish assault soared to 130,000.

Fighting raged 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 Islamic State (IS) group and allow jihadists to break out of captivity.

The Kurdish administration in northern Syria said that Turkish bombardment near a camp for the displaced led to nearly 800 relatives of IS members fleeing.

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 President Donald Trump has been accused of abandoning a loyal ally in the fight against IS after ordering US troops to pull back from the border.

The Syrian Observatory for Human Rights war monitor reported on Sunday that 14 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.

Aid groups have warned of another humanitarian disaster in Syria's 8-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 IS 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 IS," 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 IS jihadists had fled.

The SDF, a coalition of Kurdish and Arab fighters, was the main partner on the ground in the US-led campaign against IS.

Turkish President Recep Tayyip Erdogan said on Sunday that threats of sanctions and arms embargoes by Western powers would not stop Turkey's military offensive against Kurdish militants in Syria. 

"After we launched our operation, we have faced threats like economic sanctions and embargoes on weapons sales. Those who think they can make Turkey turn back with these threats are gravely mistaken," Erdogan said in a televised speech.