Kurdish authorities controlling swathes of northeastern Syria have detained alleged ISIS members from dozens of foreign countries since the jihadist group's so-called caliphate crumbled last year.
But their home countries have been overwhelmingly reluctant to claim them, with public opinion hostile to repatriating them.
On Thursday, the Kurdish authorities in northeast Syria delivered a Sudanese woman and her one-month-old baby to a Sudanese diplomat in the northeastern city of Qamishli, an AFP correspondent and an official said.
The Kurds "decided to hand her over to her country's embassy" after Khartoum requested the transfer, Kurdish foreign affairs official Abdel Karim Omar said.
"She was arrested on January 10, 2018, on the accusation of belonging to ISIS," Omar said, without providing further details.
ISIS jihadists swept across large parts of Syria and neighbouring Iraq in 2014, declaring a "caliphate" in territory they held, but have since lost most of it to various offensives.
In Syria, Kurdish fighters have formed the backbone of the Syrian Democratic Forces (SDF), an alliance backed by the US-led coalition that has expelled the jihadists from swathes of the country.
"Around 520 Daesh mercenaries, as well as 550 women and around 1,200 children from 44 countries" are still in Kurdish custody, Omar said, stressing they were all "foreigners."
"It's a heavy burden that we can't carry alone," he said.
The fate of alleged foreign ISIS members captured in Syria remains controversial, with only rare countries agreeing to take back their detainees, mostly women and children.
"We will not try any ISIS fighter," Omar said.
"We are trying as much as possible... to pressure governments to carry out their duties and take their citizens back."
Among the most infamous detainees are Alexanda Amon Kotey and El Shafee el-Sheikh, two survivors of a four-man ISIS team who carried out beheadings and were dubbed "The Beatles" because they were British.
Syria's Kurds have also captured several alleged ISIS members from France, and last month an Italian accused of being part of the jihadist group as he attempted to cross the border to Turkey.
In August, Washington said the SDF had handed over two Americans accused of supporting IS to US authorities.
Lebanese members of ISIS have also been transferred to Beirut.
