US Attorney-General Alberto Gonzales, at a news conference in Chicago, announced on Wednesday that 27 individuals from Australia, the US, Canada and England had been charged after undercover officers infiltrated a worldwide internet chat-room.
All have been charged with possession, receipt, distribution and manufacture of child pornography, and all but one have been arrested, according to authorities.
One of those arrested has been held since January, while others were arrested as recently as Tuesday. The one who is still at large is considered a fugitive, officials said.
Mr Gonzales said the chatroom, called Kiddypics & Kiddyvids, was used to trade graphic images of child pornography including live streaming video of adults sexually molesting children and infants.
"As a result of this operation, seven victims of molestation have been identified. The youngest was less than 18 months old," Mr Gonzales said.
A representative from the Australian Federal Police (AFP) was at the conference. Investigators from Canada, and the UK were also involved, Mr Gonzales said.
Abuse of minors
The attorney-general described the content in the chat-room as "the worst imaginable forms of child pornography".
"Some participants of the chat-room used minors to produce images of child pornography and then made those images, including live shows, available to other members through the internet," Mr Gonzales said.
"For example, according to the indictment announced today in Chicago, in the last year a defendant who used the screen name 'Acidburn' allegedly produced live streaming video of himself sexually molesting an infant.
"The behaviour in these chat rooms and the images many of these defendants sent around the world through peer-to-peer file sharing programs and private instant messaging services are the worst imaginable forms of child pornography."
Australian Federal Police agent Peter Drennan said the operation highlighted the international context of online child pornography and served to defeat the notion that the internet provided anonymity for offenders.
"This investigation should act as a deterrent for others who may be tempted to become involved in online child pornography," he said in a statement.