Estimates commonly put the number of imprisoned ISIS terrorists in US-SDF custody in the northeast Syria at 11,000.

Further some 70,000 family members believed linked to the former 'caliphate' are being held at the sprawling al-Hol camp, also under threat after internal camp rioting has been reported there. 

Turkey, for its part, has claimed that "YPG/PKK" forces deliberately set the Ain Issa camp on fire, denying Western reports that it came under Turkish shelling.

Meanwhile, the Trump administration has said sanctions on Turkey are "ready to go" as Erdogan has refused to uphold his "responsibilities" related to the operation, which including promises to take custody of ISIS prisoners in the area. Trump has threatened reprisals should Turkey allow even one terrorist to go free.