Dozens of suspected paedophiles are being held in synchronised raids across the world in an operation led by British police.
Officers from the UK's National Hi-Tech Crime Unit worked for a year to smash an Internet-based child abuse ring which called itself the "Shadowz Brotherhood".
Hundreds of officers swooped on suspects' homes in seven countries, seizing dozens of computers. Experienced detectives described the images and videos involved as the most horrific they had ever seen - many involved babies.
The police investigation - codenamed Operation Twins - was supported by Europol. A spokesman said around 50 suspects were involved.
Of those, 31 were in Germany although the group stretched from the UK to the US, Canada, Belgium, Denmark, Germany, Italy, the Netherlands, Romania, Spain, Sweden and Switzerland. The website was accessible via several languages.
Some members of the "brotherhood" were themselves involved in sexually abusing children and then posting the images online for others to download. Their activities centred around a website which also provided advice on how to groom children for abuse in Internet chatrooms and how to evade detection.
When uploading and downloading images to and from the site they used sophisticated encryption techniques, sometimes hiding material in seemingly innocent picture files.
The website was run by a special tier of hardcore paedophiles called "Administrators" who operated a "star" rating system. After initial vetting by an administrator new members received a "one star" rating allowing them to enter certain chat rooms newsgroups and bulletin boards.
To gain further stars they had to post images of child sex abuse for viewing and downloading by other members. As they climbed the star ladder they gained deeper access to restricted sites and password protected rooms containing the most extreme material.
PA
Patrick Logue adds:A Garda spokeswoman said Irish authorities were not involved in today's worldwide operation against paedophiles.
Last May a judge, a choirmaster and at least one school teacher were among dozens being investigated after the biggest-ever Garda operation against child pornography.
A solicitor, a barrister, a banker, a chief executive of a major company and a health board official were also among those whose homes were raided. The husband of a "high-profile Irish woman" was also believed to be under investigation.
Over 500 gardaí conducted raids at 90 addresses across the State on May 27th and seized computers and components during "Operation Amethyst".
It is understood the Garda was supplied with the names of almost 100 suspected paedophiles, who were detected using child pornography websites under observation by the FBI over the past three years.