US withdrawal from Syria leaves fate of Isis fighters and families in detention uncertain

Kurdish forces in Syria have said the fate of tens of thousands of suspected Islamic State fighters and their families is uncertain, after US forces began a sudden withdrawal from the country, abandoning their former ally on the eve of a widely-anticipated Turkish invasion.

The effects of the shock retreat continued to reverberate through the region on Monday as Turkish forces massed near the border with the Kurdish stronghold of north-eastern Syria.

Related: Latest betrayal of Kurds risks undermining defeat of Isis

The looming offensive– which was green-lighted by Donald Trump in a phone call to Recep Tayyip Erdogan late on Sunday – came as a surprise to US officials and allies, who were scrambling to understand the implications. There was a furious backlash in Congress, including from some of Trump’s closest allies, who accused the president of betraying the Kurds.

The decision represents the latest in a series of erratic moves by Trump, who is fighting impeachment at home, apparently taken without consultation with, or knowledge of, US diplomats dealing with Syria, or the UK and France, the US’s main international partners in the country.

A White House statement on Sunday night after his conversation with his Turkish counterpart said that: “Turkey will soon be moving forward with its long-planned operation into northern Syria”, adding that US forces were being removed from the area.

The Kurdish-led Syrian Democratic Forces (SDF) said on Monday its US partners had already begun withdrawing troops from areas along Turkey’s border. Footage aired on Kurdish news agency Hawar purportedly showed US armoured vehicles evacuating key positions in the border region.

The SDF spokesman, Mustafa Bali, accused the US of leaving the area to “turn into a war zone”, adding that the SDF would “defend north-east Syria at all costs”.

But on Monday the Pentagon, which has been cooperating with Turkey along the Syrian border, issued a statement saying: “The department of defence made clear to Turkey – as did the president – that we do not endorse a Turkish operation in northern Syria. The US armed forces will not support or be involved in any such operation.”

State department officials also sought to minimize the announcement, telling reporters that only about two dozen American troops would be removed from the Turkey-Syria border, and suggesting that Turkey might not go through with a large-scale invasion.

In the face of fierce criticism from both political rivals and allies in Congress, Trump took to Twitter to try to defend the move and threaten Turkey.

“I held off this fight for almost 3 years, but it is time for us to get out of these ridiculous Endless Wars, many of them tribal, and bring our soldiers home,” he said.

“As I have stated strongly before, and just to reiterate, if Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey (I’ve done before!),” he said.

It was unclear however, what was “off limits”.

In earlier tweets, Trump had appeared unsentimental about the Kurds, noting that they had been paid “massive amounts of money and equipment” in the four year campaign, when they were used as the main US proxy to fight Isis in Syria.

But the issue of Isis foreign fighters, most of them European, has clearly preoccupied the US president.

Related: Inside al-Hawl camp, the incubator for Islamic State's resurgence

Both Trump and the Kurdish-led Syrian Democratic Forces (SDF) have repeatedly called on European states to repatriate around 20,000 foreign nationals currently held in north-east Syria for trial and rehabilitation at home.

Trump argued it was up to Turkey and Europe and others, “to watch over the captured Isis fighters and families”.

An SDF spokesman, Amjed Osman, said on Monday it was not clear what would happen to the prisoners. “We repeatedly called for foreign states to take responsibility for their Isis nationals. But there was no response,” he said in a statement.

It is far from clear if Turkey has the capacity – or desire – to take custody of the detainees being held in crowded Kurdish jails and displacement camps, stretching the SDF to its limits and prompting warnings that militants are using the prisons to regroup.

Some 74,000 women and children of the caliphate are held at the infamous Hawl camp, where they are guarded by just 400 SDF soldiers. But the camp, a hotbed of violence and extremist ideology, falls outside the parameters of the 32km-deep safe zone on the Turkish-Syrian border that Erdogan has said his forces would establish.

Aid agencies warned that an offensive could displace hundreds of thousands of people, and create a new humanitarian disaster.

Save the Children said that more than 9,000 children from 40 countries were being held in camps and depended on humanitarian aid to survive.

“Reports of imminent military operations and troops already sent to the border are deeply troubling. The international community, including the UK, should take urgent steps to do what’s best for these children and bring them to their home countries before access becomes even more unpredictable,” the group said.

The Guardian understands that the SAS and French special forces present in Rojava would be tasked with securing the camp perimeters if the Kurds withdrew. However, with only several hundred troops between them, their numbers would need to be quickly boosted by regular soldiers to avoid a catastrophic collapse in security.

In Washington, the move was condemned by allies and opponents of the president. House speaker Nancy Pelosi, a Democrat, said the move “poses a dire threat to regional security and stability, and sends a dangerous message to Iran and Russia, as well as our allies, that the United States is no longer a trusted partner”.

Senate Republican leader Mitch McConnell said: “A precipitous withdrawal of US forces from Syria would only benefit Russia, Iran, and the Assad regime. And it would increase the risk that Isis and other terrorist groups regroup.”

Related: Faces of war: Kurdistan’s armed struggle against Islamic State

Republican Senator Lindsey Graham, a staunch Trump loyalist on most issues, said he would call for Turkey’s suspension from NATO and introduce sanctions against Ankara if the Turks attack Kurdish forces.

“This decision to abandon our Kurdish allies and turn Syria over to Russia, Iran, & Turkey will put every radical Islamist on steroids. Shot in the arm to the bad guys. Devastating for the good guys,” Graham wrote in a tweet.

During the campaign against Isis, the SDF did the bulk of the ground fighting to defeat Isis in Syria, losing 11,000 troops in the grinding battle. The senior ranks of the organisation are dominated by members of the Kurdistan Workers’ Party (PKK), which has fought a four-decade guerilla war against the Turkish government.

Ankara has long complained that, while fighting Isis, PKK forces were also waging war in Turkey.