US-backed forces in Syria said Wednesday they were detaining foreign Islamic State group fighters on a "daily basis", days after confirming the capture of German jihadist Martin Lemke.
AFP reported Lemke's capture last week after speaking to two of his wives who said they had fled together from IS's final holdout in eastern Syria.
The jihadists are clinging to a tiny sliver of their once sprawling "caliphate" and many residents are fleeing and turning themselves in ahead of a final offensive.
A spokesman for the Kurdish-led Syrian Democratic Forces, Mustafa Bali, said IS fighters were hiding among the fleeing civilians.
"On a daily basis, we are arresting foreign IS fighters," he told AFP, declining to provide further details on Lemke's arrest.
The SDF announced Lemke's capture in a statement posted on their website on Monday.
It said two other jihadists had also been captured, identifying them as Egyptian national Hussein Fardid and Saudi Arabian jihadist Salem al-Shamrani.
The three were detained following "two special operations" on January 25 and February 1, it added.
Investigations published in German newspapers portray Lemke, who is now believed to be 28, as an influential figure among foreign jihadists in Syria.