U.N. rights experts urged 57 states on Monday to repatriate nearly 10,000 of their citizens - women and children associated with Islamic State fighters - held in camps in northeast Syria in "sub-human" conditions without legal process.
Under international law, these states have a duty to repatriate their citizens and, if there is evidence, to prosecute adults for war crimes or other offences at fair trials in their domestic courts, the experts said.
Some 9,462 foreign women and children are among more than 64,600 people detained at al-Hol and Roj camps, run by Syrian Kurdish authorities, where the majority of residents are Iraqi and Syrian nationals.
"The matter is one of extreme urgency," Fionnuala Ní Aoláin, U.N. special rapporteur on protecting human rights while countering terrorism, told a news briefing after the independent experts issued a joint statement.
She called the list of 57 countries - which include Britain, China, France, the Russian Federation and the United States - a "list of shame". She also decried "an uptick in nationality stripping", noting it was unlawful to leave someone stateless.
"These women and children are living in what can only be described as horrific and sub-human conditions... The conditions in these camps may reach the threshold of torture, inhuman and degrading treatment under international law," Ní Aoláin said.
Some women had been "groomed online" as brides of Islamic State fighters, while children "had no say in what brought them there", she said.
The United Nations said last month it had received reports of 12 Syrian and Iraqi nationals being murdered in the first half of January at al-Hol camp, which holds internal refugees and families of Islamic State fighters.
Canada, Finland and Kazakhstan have repatriated some nationals, Ní Aoláin said, welcoming "the trickle of returns".
She compared the "illegal detention" to that of security suspects held at the U.S. detention facility in Guantanamo Bay for years without charge.
"These women and children are a convenient battering ram on all the fears of state and the public. They are made objects of hate, ridicule and shame," she said.