German cops have arrested a man in a shocking case of a four-year-old girl who was being abused on the dark web.

The suspected abuser was turned in by the girl's mum and grandparents after authorities took the unusual step of going public with images of the young victim yesterday (9 October) in a bid to identify her.

Before midnight yesterday both the victim and abuser had been identified and a 24-year-old man from Lower Saxony is now in custody.

The photos of the female victim had been released with an urgent appeal for information about who she is.

Degrading pictures of her suffering were uploaded to the dark web by her tormentor – and the images are said to have sickened hardened lawmen.

Police said she was subjected to "serious sexual abuse" between October last year and July this year.

Chief prosecutor Georg Ungefuk from the Central Office for Combating Cyber Crime told Bild newspaper: "The suspect was arrested in the evening hours by the state police in an apartment. He is a German citizen. The man is being questioned."

Ungefuk took the decision to release the images of the girl on Monday stating: "This is the last measure to identify the perpetrator. We only fell back on this as all other possibilities have not led to finding out who she is."

He added: "The girl is also German and four years old. It was examined by a police psychologist and is now again in parental care."

It is unclear whether the victim is related to the suspect.