United Nations human rights experts urged Switzerland on Thursday to repatriate two Geneva sisters from a squalid camp in north-eastern Syria five years after the girls were allegedly abducted by their mother who joined Islamic State (IS). A senior Swiss foreign ministry official said it was working hard to have the girls repatriated. The mother"s Swiss nationality had been withdrawn for security reasons, but she has other nationalities, he said. "We have been working intensely on this case. We are trying to have the girls repatriated but it takes time. In the meantime we have contributed to more acceptable living conditions for them in the camp and have also organised telephone calls with their fathers," Johannes Matyassy told Reuters. More than 60,000 people, two-thirds of them children, are held in camps for families associated with IS fighters, which the head of the International Committee of the Red Cross described after a visit in March as a "tragedy in plain sight". read more The al-Hol and al-Roj camps, run by Syrian Kurdish forces, hold nationals from some 60 countries who fled IS"s final enclaves. "The two fathers of the girls, who both live in Geneva, have asked the Swiss government to take the necessary steps to repatriate their daughters, who were ostensibly taken by their mother on a vacation in August 2016 but ended up in Syria," the U.N. experts said in a statement. "The repatriation of these two children should not be further delayed," they said, adding that the half-sisters were held at al-Roj. The 14-year-old has anaemia and is believed to have suffered a severe shrapnel wound to her leg, requiring three operations, while the eight-year-old was thought to be in poor health. The Swiss foreign ministry reaffirmed its 2019 policy on "travellers motivated by terrorism", which puts Swiss security first. Repatriation can only be considered for minors in such situations, but some mothers refuse to be separated, it said. The fathers, through their lawyers, have written to Swiss parliamentarians seeking support for the girls" repatriation.