A man who allegedly posed as Justin Bieber online to solicit explicit images from children - including up to 20 from the UK - has been charged with more than 900 child sex offences.
Gordon Douglas Chalmers, a law lecturer at Queensland University of Technology in Brisbane, Australia, faces 931 offences dating back a decade, including rape and making child exploitation material.
The 42-year-old is said to have used Facebook and Skype to impersonate the singer and contact children, Australian police said.
Officers in Queensland said the offences are believed to involve 151 alleged victims, including up to 20 British children and 50 from the US.
Police are urging Bieber fans - known as "Beliebers" - and their parents to be vigilant while using the internet following the charges.
Chalmers was held after tip-offs from US and German authorities.
He had been charged in November with "a number of child sex offences" including grooming and possessing explicit material.
After a "thorough examination" of his computer, a large amount of material was seized and he was charged with more than 900 further offences dating back to at least 2007, Queensland Police said.
The additional charges include rape, indecent treatment of children and making child exploitation material.
Detective Inspector Jon Rouse said: "This investigation demonstrates both the vulnerability of children who are utilising social media and communication applications and the global reach and skill that child sex offenders have to groom and seduce victims.
"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.
"The breadth of offences committed in this instance are frankly horrendous and I want to recognise the efforts and commitment of the investigative team at Taskforce Argos to keeping children safe."
Bieber kicked off the Australian and New Zealand leg of his Purpose world tour on Monday.
Chalmers will appear at Brisbane Magistrates Court on April 6.
A National Crime Agency spokesman said: "We are aware of reports that a small number of victims in this case may be in the UK and we are liaising with police in Australia.
"There are many ways in which people engage with each other online and we know that those with a sexual interest in children will seek to exploit tools such as social media for their own ends."