Ankara, which has criticized Western countries for not taking back Islamic State group (IS) fighters
UN chief Antonio Guterres called on Tuesday for an international accord on the fate of foreign jihadists being held in the Middle East, saying it was not up to Syria and Iraq "to solve the problem for everyone."
"We need international cooperation to solve the problem," Guterres, who is attending the Paris Peace Forum alongside some 30 world leaders, told France's RTL radio.
"We cannot just ask Iraq and Syria to solve the problem for everyone. There must be real international solidarity," he said.
Ankara, which has criticized Western countries for not taking back Islamic State group (IS) fighters, on Monday began deporting foreign jihadists being held in Turkish prisons to their countries of origin.
The deportations come after Turkey came under fierce criticism from some of its Nato allies, including France and Germany, over its offensive last month against a Kurdish militia in northeast Syria that had been helping the US combat IS.
Kurdish forces have warned that the Turkish incursion could embolden IS, helping the insurgents to regroup after they lost their so-called caliphate in Iraq and Syria.
"If everyone starts using these people against each other, we will inevitably see terrorists freeing themselves and doing dangerous things," Guterres said.
Syrian Kurdish forces are holding thousands of foreign jihadists in prisons across northeast Syria, and thousands more wives and children of the fighters are being kept in camps for the displaced.
European countries have so far been reluctant to take back jihadists or their families, fearing they could pose a security threat, even if jailed.
France's foreign minister last month travelled to Baghdad to try to convince Iraq to take in foreign jihadists from Syria and put them on trial there.
Guterres said that in his opinion Western countries should take back the women and children and help re-integrate them into society.