The US is reported to have taken custody of two British Isis members accused of involvement in the beheading of western hostages, ahead of a Turkish offensive on the Kurdish region of Syria where they were being held.
The two men, Alexanda Kotey and El Shafee Elsheikh, members of a British group of Isis militants known as "the Beatles" had been at the centre of a legal battle in London. It is being led by Elsheikh's mother who went to court in London to stop his extradition to the US, and to prevent the British government sharing evidence with the US, if the death penalty is not ruled out.
The Washington Post reported on Wednesday evening that the two men had been transferred to US custody because the Turkish invasion into northeastern Syria threatened their continued detention by the Kurdish-led Syrian Democratic Forces (SDF).
Related: Turkish troops advance into Syria as Trump washes his hands of the Kurds
UK and US officials refused to comment on the report but in remarks earlier on Wednesday, Donald Trump said: "We have taken a certain number of Isis fighters that are particularly bad, and we've wanted to make sure that nothing happened with them with respect to getting out."
Trump said he had talked to Boris Johnson on the subject of Isis prisoners, but did not say whether he was referring to Kotey and Elsheikh.
Earlier this month, a cross-party group of MPs and peers who visited the region last month warned that Trump's green light to a Turkish invasion "risks global security" because it could allow Isis members to escape and regroup.
Meanwhile, women and children in the largest Islamic State detention centre in Kurdish-controlled Syria are expecting to be freed in the wake of a Turkish assault on the area, according to people inside the camp.
Al-Hawl, home to about 60,000 women and children with links to Isis and 10,000 displaced civilians, has been tense since Donald Trump announced US troops would leave the area at the weekend, paving the way for the Turkish attack on Wednesday.
Radicalised women, including some who have been accused of killing other prisoners they say are not adhering to Isis's strict ideology, believe Isis sleeper cells in the area will attack the Kurdish guards and free those inside in the next two days, a woman who has been held alongside them said via WhatsApp message.
"They know the Turkish campaign has begun," the woman said. "After living in this horrible place for months they are ready to take this opportunity to break out."
About 90,000 men, women and children from Isis' former "caliphate" are currently in the custody of the US-backed Kurdish-led Syrian Democratic Forces (SDF). Their fate was thrown into question by Trump's announcement that he would withdraw the 1,000 US special forces in the area, effectively removing the buffer that has stopped Turkey attacking the SDF.
Related: Inside al-Hawl camp, the incubator for Islamic State's resurgence
In rambling remarks on Isis detainees, the US president railed against European countries for not taking custody of their own nationals who had been caught in Isis ranks.
"I gave them one chance, I gave them another chance, I gave them a third chance and even gave them a fourth chance. They didn't want to take them back," Trump complained. He argued that if European governments had complied with his request they would not be facing the risk of escaped Isis fighters returning to their homelands.
"Well, they're going to be escaping to Europe. That's where they want to go. They want to go back to their homes, but Europe didn't want them from us," the president said.
European officials insist that Trump's response to Recep Tayyip Erdoğan's request for acquiescence in his planned offensive might have been based, at least in part, on a misunderstanding of the status of the Isis prisoner issue.
At the time the Turkish offensive began, the US, France, Germany and other European countries whose nationals had joined Isis had been exploring ways of prosecuting Isis fighters in the region, most likely in Iraq. It was officially called the "regional prosecution pathway".
"We never expected the US to take them back on to US soil, and we definitely did not want them taken to Guantanamo," a European official said, expressing surprise at the president's remarks, as the Europeans and the US had been in constant and continuing discussions about the fate of the Isis captives.
The official said the reason European fighters were not being taken back by their own countries was not about cost, but about the difficulties of prosecuting them.
"It is a question of due process," the official said. "Courts at home would throw out cases of detainees captured on the battlefield."