Turkish forces approached a key Kurdish-held town in northern Syria on Sunday, setting off clashes that allowed hundreds of ISIS supporters to escape from a camp for displaced people near a U.S.-led coalition base, Syrian Kurdish officials said.

A U.S. military official said the situation across northeastern Syria was "deteriorating rapidly" and American forces no longer control ground communications with the Syrian Kurdish fighters with whom they had previously partnered. The official, who was not authorized to disclose operational details and spoke on condition of anonymity, said U.S. troops on the ground are at risk of being "isolated" and could clash with Turkey-backed Syrian forces.

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

France's president said on Sunday he had told Turkish President Tayyip Erdogan and U.S. President Donald Trump in telephone calls that the Turkish offensive in Syria had to stop immediately and it risked creating a humanitarian crisis.

"We have a common desire that this offensive ends," Emmanuel Macron said alongside Germany Chancellor Angela Merkel. "This offensive risks creating an unsustainable humanitarian situation and to help Islamic State re-emerge in the region."

Erdogan on Sunday dismissed the reports of camp escapes, saying they were "disinformation" aimed at provoking the West.

Erdogan was quoted by the state-run Anadolu news agency as saying these reports were false and aimed at provoking the United States.

Warplanes strike villages, war monitor says

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.

The Kurdish-led Syrian Democratic Forces (SDF) were a key U.S. ally in the war against the Islamic State in Iraq and Syria, and drove the extremists from most of the territory they once held in northeastern Syria. The force swept up thousands of ISIS fighters and their family members in the campaign, and has warned it may not be able to maintain its various detention centres as it struggles to repel the Turkish advance.

This explosion on Saturday over the Syrian town of Ras al-Ayn was seen from the Turkish border town of Ceylanpinar, Sanliurfa province. (Stoyan Nenov/Reuters)

NATO member Turkey views the Kurdish fighters as terrorists because of their links to the insurgency in its southeast and has vowed to carve out a "safe zone" along the border. It launched the operation earlier this week after Trump moved U.S. forces aside, saying he was committed to getting out of America's "endless" wars.

Amid growing chaos in Syria, Trump has ordered all U.S. troops to withdraw from the country's north to avoid an "untenable" conflict between Turkey and U.S.-backed Kurdish fighters, Defence Secretary Mark Esper said Sunday.

The approximately 1,000 U.S. troops in Syria are not leaving the country entirely, Esper told CBS's Face the Nation.

Esper said he spoke to Trump on Saturday night amid growing signs that the Turkish invasion is growing more dangerous.

"In the last 24 hours, we learned that they [the Turks] likely intend to expand their attack further south than originally planned — and to the west," Esper said.

Trump, in a tweet Sunday, said: "Very smart not to be involved in the intense fighting along the Turkish Border, for a change. Those that mistakenly got us into the Middle East Wars are still pushing to fight. They have no idea what a bad decision they have made. Why are they not asking for a Declaration of War?"

Esper said he would not discuss a timeline for the U.S. pullback, but it would be done "as safely and quickly as possible." Esper isn't saying how many U.S. troops will leave the north, but they represent most of the 1,000 troops in Syria.

He also said it appears the U.S.-backed Kurdish forces are trying to "cut a deal" with the Syrian army and Russia to launch a counterattack against the Turks.

Tens of thousands of Syrians flee

The United Nations says more than 130,000 Syrians have fled since the operation began five days ago, including many who had taken refuge from previous rounds of fighting in the country's eight-year civil war.

Turkey's Defence Ministry tweeted Sunday its forces had taken control of the main highway running between Hassakeh, a major town and logistics hub, and Ein Eissa, the administrative centre of the Kurdish-held areas.

Heavy fighting was also underway Sunday in the town of Suluk, northeast of Ain Eissa.

Turkey's official news agency said Syrian fighters allied with Ankara had captured the town, while Kurdish officials said they were still battling to hold onto it. The Anadolu news agency said Turkey-backed forces had cleared the town centre of Suluk, which is located at a strategic crossroads about 10 kilometres south of the border.

Turkish troops and their Syrian allies have made steady gains since launching the operation, capturing several northern villages in fighting and bombardment that has killed and wounded dozens of people. The military said it captured the centre of the sizable town of Ras al-Ayn Saturday. Turkey continued shelling around the town and sporadic clashes could be heard.

UN says pumping station shelling affects water supply

Turkey's Defence Ministry tweeted that 480 Kurdish fighters were "neutralized" since Wednesday. The number could not be independently verified.

The clashes have spilled across the border, with shells fired from Syria hitting the Turkish border towns of Akcakale and Suruc. Anadolu says one person was wounded in Suruc on Sunday.

Heavy outgoing shelling could be heard in Akcakale early Sunday and at least one incoming projectile hit a house, leaving a gaping hole in the exterior wall and rubble inside. It was not immediately clear if anyone was wounded. Police collected evidence as a crowd gathered outside.

The UN, meanwhile, said a pumping station in the town of Hassakeh was damaged by shelling, affecting the water supply for 400,000 people, including 82,000 residents of camps for displaced people.

Erdogan said Friday that Turkey won't stop until the Syrian Kurdish forces withdraw beyond a 32-kilometre line from the border.