More than 100 Islamic State prisoners have escaped in Syria: US envoy

More than 100 prisoners of the Islamic State extremist movement have escaped in Syria in the chaos since Turkey's incursion, a senior US official said Wednesday.

"We would say the number is now over 100. We do not know where they are," James Jeffrey, the State Department pointman on Syria, told the House Foreign Affairs Committee when asked about the detainees.

Turkey launched a military operation in Syria after President Donald Trump agreed to pull US troops who were allied with the Syrian Democratic Forces, the Kurdish-led group that bore the brunt of the fight against the Islamic State group.

Jeffrey said the Kurdish fighters were still guarding prisoners from the extremist group, despite their warnings that they will need to devote resources to fighting Turkey instead.

"Almost all of the prisons that the SDF were guarding are still secured. The SDF still has people there," Jeffrey said.

"We are monitoring that as best we can. We still have people in Syria working with the SDF and one of those priorities is these prisons," he said.

The remarks nevertheless appeared at odds with Trump's claim on Twitter earlier that "Kurds are safe and have worked very nicely with us. Captured ISIS prisoners secured."