According to the Norwegian prosecution, the man targeted and assaulted several hundred teenagers aged 9 to 21 by posing as a woman on the internet.

Norwegian authorities have charged a man in his twenties, identified as a football referee, with sexual offences involving some 300 teenage boys in Norway and fellow Scandinavian countries since 2011, the biggest such case in the country's history, national broadcaster NRK reported.

The man allegedly targeted boys on the internet, where he adopted female personas in serveral chat services and convinced the victims to engage in sexual acts, which he filmed, with promises of money and/or erotic photos in return. The prosecutor's office said that the victims were aged 9 to 21. The charges include rape.

"The case is a serious one, and it is the biggest case of sexual abuse in Norway to date," state prosecutor Guro Hansson Bull said in a statement.

Attorney General Christian Lundin said this case was 'incomparable' in Norway's legal history.

While posing as a woman, the man allegedly initiated sexual conversations and made young boys masturbate on camera, promising suggestive images in return. The man also threatened several of his victims with publishing the films on the internet, if they stopped sending them. In total, the man received and saved at least 16,463 unique films, according to the indictment.

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Many of the victims live outside Norway, which prompted extensive collaboration with Swedish and Danish police officers.

"Virtually all the victims are struggling with this case because they have a large sense of guilt," Lundin stressed.

Of all of the men's victims, only two reported the case to the police, which according to Hansson Bull signals how difficult it is to admit this sort of crime.

According to the man's lawyer Gunhild Lærum, he 'admitted the facts' and said he was 'sorry', but has yet to respond to each charge individually.

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The man was arrested and briefly sentenced in the summer of 2016, but was released shortly afterward. Since then, he committed new assaults before being arrested again.

The trial will be held in 2019.