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BRISBANE, Australia — Fans of Justin Bieber and their parents were warned to be vigilant on the internet after a man who allegedly posed as the pop star online was charged with more than 900 child sex offences.

Gordon Douglas Chalmers, a 42-year-old law lecturer at the Queensland University of Technology, is accused of pretending to be Bieber and soliciting explicit images from children.

"The breadth of offenses committed in this instance is frankly horrendous."

Chalmers was charged in November with using Facebook and Skype to impersonate the singer, after tip-offs from U.S. and German authorities. Chalmers was charged with using a carriage service to procure and groom children for sex and to access child pornography. He was also charged with possessing child porn.

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As a result of warrants issued in November to search his social media and messaging accounts and cloud servers, Chalmers was charged this week with another 931 child sex offenses dating back a decade, including rape and making child exploitation material, a police statement said.

Justin Bieber OCESA/CHINO LEMUS HANDOUT / EPA

"The fact that so many children could believe that they were communicating with this particular celebrity highlights the need for a serious rethink about the way that we as a society educate our children about online safety," Police Detective Inspector Jon Rouse said in a statement. "The breadth of offenses committed in this instance is frankly horrendous."

Bieber has more than 92 million followers on Twitter.

Police have not said how many children had become victims or revealed which countries they live in. But Rouse said the investigation showed "the global reach and skill that child sex offenders have to groom and seduce victims."

Chalmers has yet to enter pleas.

Bieber, 23, is currently touring Australia.