The Kurdish-led administration in northern Syria has called for the creation of an international tribunal to try thousands of suspected members of the Islamic State (IS) group.
One official, Abdul Karim Omar, told the BBC they were struggling to cope with the thousands who emerged from the last IS enclave of Baghuz, in the east.
Kurdish-led Syrian Democratic Forces (SDF) captured the village last week.
About 1,000 foreign fighters are among the thousands held by Kurds in prisons.
The men are said to come from some 50 countries.
US President Donald Trump hailed the capture of Baghuz although he said the US would “remain vigilant” as the group remains a threat.
At its height, IS controlled 88,000 sq km (34,000 sq miles) across Syria and Iraq.
While it no longer holds this territory, US officials believe IS may have 15,000 to 20,000 armed adherents active in the region, many of them in sleeper cells, and that it will return to its insurgent roots while attempting to rebuild.
What did the Kurds say?
In a statement, the Kurdish administration called for “a special international tribunal in north-east Syria to prosecute terrorists” to ensure that trials are “conducted fairly and in accordance with international law and human rights covenants and charters”.
Speaking to the BBC, the administration’s head of foreign affairs, Abdul Karim Omar, said the fact so few nations had repatriated their citizens who joined IS has added to their problems.
Many Western governments have refused to repatriate their citizens amid concerns over the potential security risks they may pose, as well as the challenges of gathering evidence to support prosecutions.
The US-backed SDF forces have reportedly captured more than 5,000 militants – from Syria and abroad – since January and put them in detention centres, while women and children are kept in camps for the displaced.
According to one Kurdish official speaking to AFP news agency, more than 9,000 foreign relatives of IS members – many of them children – are being held at the Kurdish-run al-Hol camp. The accommodation was built for about 20,000 people but is now housing more than 70,000.