ROME (AFP) - A British model was drugged and abducted for a week in Italy last month by a British-based Pole who allegedly tried to auction her off as a sex slave on the dark web, Italian police said on Saturday (Aug 5).

The unidentified 20-year-old was injected in the arm with the tranquiliser ketamine after going to what was a fake photo shoot at a venue near Milan's central station on July 11.

Her kidnapper and an accomplice allegedly stripped, photographed and bound the woman before driving her in the boot of a car from Milan to a country house in the tiny village of Borgial in the northwestern region of Piedmont.

Lukasz Pawel Herba, 30, has been charged with orchestrating the kidnapping and given a version of events which the prosecutor in charge of the case described as barely credible.

Detectives are unclear as to whether Herba was serious about auctioning his victim or if it was simply a threat intended to extort €300,000 (S$480,000) in Bitcoin from the model's agent and family.

No one took part in the online auction, so it was unclear if Herba had the necessary contacts to organise such an operation of was something of a fantasist, according to the police.

"Fantasist or not, what is clear is that he is a very dangerous man who drugged his victim as soon as she was kidnapped and put her inside a large travel bag in the boot of a car," Milan deputy prosecutor Paolo Storari told a press conference.

"His version of events is barely credible but clearly he does not deny that he was with her for the time she was missing," Storari said.

On July 17, for reasons that are not clear, Herba drove the woman back to Milan and released her close to the British Consulate, where he was arrested.

He had told the model that he could not go on holding her because she was a mother of a young child and such abductions were prohibited by "Black Death", a nefarious web-based group he claimed to belong to.

Police said they were not sure if the group actually existed.