The US is withdrawing all its troops from northern Syria as Turkey advances its operation against the Kurds.

Defence Secretary Mark Esper said Turkey “likely intends” to extend its attack further than originally planned.

The assault is aimed at forcing out Kurdish forces – the main US ally in the area. They may be seeking help from Syria and Russia, said Mr Esper, and the US would not be defending them.

Syria has now announced it is sending troops north to face Turkish forces.

More than 130,000 people have fled homes near the conflict, the UN said, warning the figure could soon triple.

The Syrian Democratic Forces (SDF), the Kurdish-led fighters under attack from Turkey, warned last week that they would no longer be able to guard suspected IS members and their families in camps and prisons under their control if the Turkish offensive continued.

And on Sunday, Kurdish officials said nearly 800 relatives of foreign IS members had escaped from Ain Issa, a camp in the north, as clashes raged nearby.

Read more:   Gerard Pique handed 2.1 million tax bill 

The Turkish offensive, which started last week, has drawn an international outcry, as the SDF were the main Western allies in the battle against Islamic State in Syria.

But Turkey views the Kurdish groups within the force as terrorists and says it wants to drive them away from a “safe zone” reaching 30km into Syria.

It plans to resettle more than three million Syrian refugees currently in Turkey within the zone – many of whom are not Kurds. Critics have warned this could lead to ethnic cleansing of the local Kurdish population.

Turkish-backed Syrian rebels watch the border town of Ras al-Ain on October 12, 2019, during their assault on Kurdish-held border towns in northeastern Syria.

Turkish-backed Syrian rebels watch the border town of Ras al-Ain on October 12, 2019, during their assault on Kurdish-held border towns in northeastern Syria. Photo: AFP

The situation in Syria is becoming “very untenable”, US Defence Secretary Mark Esper told CBS’s Face the Nation on Sunday.

“In the last 24 hours, we learned that the Turks likely intend to extend their attack further south than originally planned, and to the west,” he told CBS’s Face the Nation.

Read more:   NASA wants international partners to go to Moon too  

President Recep Tayyip Erdogan said on Sunday the aim of the incursion was to establish a “security zone” that would extend from Kobane in the west to Hassakeh in the east, about 30km deep into Syrian territory.

While he said this was “in line” with the safe zone map originally proposed, Hassakeh lies more than 70km away from the Turkish border.

Mr Esper said the decision to withdraw remaining US troops from northern Syria was made after discussions with his national security team and US President Donald Trump.

He was unable to give a timeframe for the withdrawal and did not specify where the troops would be moved to next.

Mr Esper said the SDF were “looking to cut a deal” with the Syrian government and its Russian allies to counter the Turkish attack which , would leave the US forces stuck between “two opposing advancing armies”.

Read more:   New round of talks on Syria to be held in Geneva in mid-June

Hours after his comments, the Syrian army was reported by state media to have been deployed to the north to “confront a Turkish aggression” on Syrian territory. It is not yet clear where exactly the troops are being sent.

President Trump’s decision last week to move some of his troops from pockets in the north-east of Syria effectively paved the way for the Turkish operation against the Kurdish fighters, who have lost the protection of their US allies.

On Sunday, he tweeted that it was “very smart” not to be involved in the fighting “for a change”.

More than 50 civilians and over 100 Kurdish fighters killed in north-eastern Syria, according to the Syrian Observatory for Human Rights.

The Syrian Democratic Forces say the Kurdish forces’ death toll is 56 and Turkey gives a higher figure of 440

Eighteen civilians killed in southern Turkey, according to Turkish reports, while 20 soldiers or pro-Turkish fighters were killed in Syria.