Turkish forces approached a key Kurdish-held town in northern Syria on Sunday, setting off clashes that allowed hundreds of Islamic State supporters to escape from a camp for displaced people and prompted US soldiers to withdraw from a nearby base.

A US military official said the situation across northeastern Syria was deteriorating rapidly and that American forces were cut off from the Syrian Kurdish fighters they had previously partnered with. The official, who was not authorised to disclose operational details and spoke on condition of anonymity, said US troops on the ground are at risk of being isolated and cannot travel overland without a high risk of armed confrontation with Turkey-backed forces.

The camp in Ein Eissa, some 35 kilometers south of the border, is home to some 12,000 people, including 1,000 wives and widows of Islamic State fighters and their children. The Kurdish-led administration in northern Syria said in a statement that 950 IS supporters escaped after attacking guards and storming the gates. It was not immediately possible to confirm that figure.

The Britain-based Syrian Observatory for Human Rights said Turkish warplanes struck villages near the camp on Sunday. It said camp residents fled as clashes broke out between Turkey-backed Syrian fighters and Kurdish forces, without providing an exact number.