BORIS Johnson has urged President Recep Tayyip Erdogan to halt Turkey’s military assault on Kurdish-held northern Syria.

In a telephone call to the Turkish leader, the Prime Minister voiced his “grave concern” that the action could worsen the humanitarian situation in the region and undermine the fight against Daesh.

He called on him to enter into dialogue with a view to reaching agreement on a ceasefire, as Erdogan yesterday ruled out mediation.

“He expressed the UK’s grave

concern about Turkey’s military operation in northern Syria which he said could further worsen the humanitarian situation there and undermine the progress made against Daesh ,” a No 10 spokesman said.

“The Prime Minister underlined that Turkey is an important partner for the UK and a Nato ally.

“He recognised Turkey’s role at the forefront of the fight against Daesh and its generosity in supporting refugees who’ve fled the civil war in Syria.

“But the Prime Minister was clear that the UK cannot support Turkey’s military action.

“He urged the president to end the operation and enter into dialogue, and said the UK and international partners stand ready to support negotiations towards a ceasefire.”

The incursion against the Syrian Kurds – who played a key role in dismantling the Daesh caliphate but are regarded as terrorists by Turkey – has been widely condemned in the West,

It comes days after President Donald Trump cleared the way for Turkey’s air and ground offensive, pulling back US forces and saying he wanted to stop getting involved with “endless wars”.

His decision has drawn heavy criticism in the US amid accusations he was endangering regional stability and risking the lives of Syrian Kurdish allies.

There are concerns that hundreds of suspected Daesh prisoners, including foreign fighters being guarded by Kurdish forces, may escape during the chaos.

As the Turkish incursion entered its fourth day yesterday, its forces approached a key Kurdish-held town in northern Syria, setting off clashes that allowed hundreds of Daesh supporters to escape from a camp for displaced people.

The move also prompted US soldiers to withdraw from a nearby base.

A US military official said the situation across north-eastern Syria was “deteriorating rapidly” and that American forces were cut off from the Syrian Kurdish fighters they had previously partnered with.

They added that US troops cannot travel overland without a “high risk” of armed confrontation with Turkey-backed forces.

The camp in Ein Eissa, around 20 miles south of the border, is home to some 12,000 people.

The Kurdish-led administration in northern Syria reported that 950 Daesh supporters escaped after attacking guards.

Jelal Ayaf, a senior official at the camp, said 859 people successfully escaped from the section housing foreigners. He said a few were recaptured but that supporters inside the other section of the camp also escaped and were carrying out attacks.

The US official said a “small group” of American troops withdrew from a base in the town because of the threat posed by Syrian fighters allied with Turkey, but that US forces were still present in larger bases nearby.