The Syrian Democratic Forces (SDF) detained German extremist Martin Lemke after he fled the last pocket held by the "Islamic State of Iraq and Syria" (ISIS) in Syria, two of his wives said Thursday (January 31st).

His third wife, a German national who gave her name as Leonora, told AFP at a screening centre in Deir Ezzor that Lemke, his second wife and herself fled the fighting together.

"We gave up together," the 19-year-old said in English, adding that Lemke arrived with her at the centre run by the SDF, where many have been turning themselves in before a final offensive.

The SDF separate civilians from suspected active ISIS members during the screening.

Leonora said Lemke had a health problem which meant he could not fight and claimed he had worked mostly as a technician for ISIS.

However, investigations published in German newspapers portray Lemke, who is now believed to be 28, as an influential figure among foreign extremists in Syria.

A report in German newspaper Die Zeit in December 2017 said Lemke arrived in al-Raqa in November 2014 and joined the group's hesba ("religious police"). He is then believed to have become a member of ISIS's intelligence service.