News of Germans' involvement in torture comes from testimony from former Isis fighter Nils D., originally a part of the infamous Salafist (Sunni fundamentalist) scene in Dinslaken-Lohberg, North Rhine-Westphalia, the Süddeutsche Zeitung (SZ), NDR and WDR reported.
Nils D. was in Syria for 13 months between October 2013 and November 2014, spending eight of them in a unit known as the “assault squad” responsible for capturing deserters and “deviators”.
These jihadists always went masked in public and received better salaries and bonuses from Isis for their work, including looted trophies from the Iraqi city of Mosul.
Nils D. said that a number of other Germans remain active in the unit, which is known to German authorities as the "internal security department" of Isis.
The prison in Manbij, Syria, where Nils D. worked subjects its prisoners to torture until they admit to their supposed crimes.
Manbij also boasts an "execution square" in the town where public shootings and beheadings take place.
Nils D. said that an Isis commander was once executed there as an example to others.
He himself claims not to have been involved in executions or torture, saying that he served only as a guard for informants and as a cook in the prison.
But a photo found on his mobile phone shows him holding a weapon against the back of a prisoner's head, the SZ reported.
That was seized in evidence after police eavesdropping caught Nils D. talking to a fellow Islamist about his experiences after his return to Dinslaken in late 2014.
He is set to face trial beginning in January 2016 in Düsseldorf.