LONDON • The 26-year-old man pretended to be a teenage girl to meet boys and young men on online chat forums.
He called himself "Sandra" or "Henriette", met boys from Norway, Sweden and Denmark, and asked them to send explicit images and videos, prosecutors said.
After they complied, he threatened to publish the footage on YouTube if they did not keep the images coming. He also talked a few into meeting in person. Then, officials said, he raped some of them.
The Norwegian man - identified only as Henrik, a soccer referee - was charged last Friday with sexually abusing more than 300 boys in three countries beginning in 2011. The authorities found more than 16,000 explicit films of victims on the suspect's computer.
The scale of the abuse in this "catfishing" case prompted a lawyer for the victims to describe it as "incomparable in Norwegian legal history".
"This is the largest case of abuses that has ever been uncovered, with an enormous scope and harsh acts," Mr Christian Lundin, the main lawyer representing victims in the case, said in an e-mail. The case is set to go to trial on Jan 22.
Mr Guro Hansson Bull, one of the three prosecutors handling the case, said last Thursday: "The indictment is 81 pages long and covers a range of different sexual offences, including rape."
The large number of victims was possible because of only one thing: the perpetrator having access to children online.
Under Norwegian criminal law, sexual abuse over the Internet is legally the same as physical sexual abuse, and the number of online sexual offences is increasing as more young people get access to smartphones and the Web, according to the authorities.
Reports to police of criminal sexual acts against children under 16 rose to 833 from 227 between 2004 and last year, according to the Norwegian Statistical Bureau.