(AFP) -- The US-backed Syrian Democratic Forces (SDF) said over 3,000 civilians had left Raqqa on October 14 as part of a deal negotiated between officials from the provisional Raqqa Civil Council and Syrian Isis fighters.
The US-led coalition later acknowledged that of these up to 300 were seen as "potential" Isis fighters, following a BBC report that hundreds of terrorists, including foreigners, had left as part of the deal.
Isis lost control of Raqqa on October 17 after months of fighting against the SDF, a Kurdish-dominated force regarded with disdain by Turkey.
The Turkish foreign ministry described the information as an "extremely grave and eye-opening revelation", accusing the SDF of negotiating with Isis to evacuate fighters.
The SDF is dominated by the Syrian Kurdish People's Protection Units (YPG), which Ankara views as a "terror" group linked to the outlawed Kurdistan Workers' Party (PKK) waging an insurgency inside Turkey.
Ankara has long lambasted Washington for working with and arming the YPG as the main US ally in the fight against Isis.
- 'Terror corridor' -
The ministry said the purpose of the YPG was not to fight Isis "but to create illegitimate faits-accomplis on the ground, to occupy territories and to alter their demographic structures," the ministry said.
President Recep Tayyip Erdogan has vowed he would not allow a "terror corridor" controlled by the YPG in Syria close to Turkey's border.
He has also warned that Turkey could yet mount a military operation against the YPG to oust the group from the northern Syrian town of Afrin.
Concerns over the Raqqa deal came to the fore this week after the BBC reported on Monday that hundreds of Isis fighters, including foreigners, had left Raqqa in a massive convoy assembled on October 12.
But at the time the US-led coalition against Isis said it was "very adamant" that foreign Isis fighters not be allowed to leave Raqqa.
Coalition spokesman Colonel Ryan Dillon said on Tuesday that "out of the 3,500 civilians that came out of... Raqqa at that time, approximately less than 300 were identified and screened as potential (Isis) fighters."
Turkey has suffered a series of attacks blamed on Isis militants over the past two years, the latest in January at an elite Istanbul nightclub during which an Isis gunman killed 39 people.
(Photo: AFP)