Austria has uncovered an international child pornography network involving more than 2,360 suspects from 77 countries, the interior minister said.
The suspects paid to view images that showed "the worst kind of child sexual abuse", Guenther Platter said.
The videos were posted on a Russian website, hosted by an Austrian company.
No arrests have yet been made but Austrian authorities are sharing their information with investigators in other countries including the US and Germany.
Austrian federal police said the case was "a strike against child pornography unprecedented in Austrian criminal history".
Twenty-three suspects were being questioned, Austrian officials said, and arrest warrants might soon be issued. Fourteen of them have confessed to downloading the material.
The youngest person implicated was 17 and the oldest was 69. They included students, government employees and retired people, Mr Platter said.
He said the FBI was investigating some 600 suspects in the US. German authorities were following leads on at least 400 people, France was looking into about 100 more and Britain was investigating 72 people.
Denmark's news agency Ritzau said 19 Danes were involved in the investigation, according to police sources.
Downloads of the illegal videos were recorded in countries ranging from Algeria to Iceland and Venezuela - those under investigation are suspected of distributing the material after watching it.
The inquiry began in July after an Austrian internet service provider notified police that unauthorised video files had been uploaded on to its server from London.
The material was accessible via a link to a Russian website that offered it for downloading - the site has since been closed down.
Within 24 hours, investigators said they recorded more than 8,000 hits on the video and DVD material from more than 2,360 computer addresses in 77 countries.
Harald Gremel, an Austrian police expert on internet crime who led the investigation, said the videos were made in eastern Europe and featured children of up to 14 years of age.
"Girls could be seen being raped, and you could also hear screams" Mr Gremel said, adding that users paid $89 (68 euros, £45) for three month's access to the material.
Under Austria law, the maximum prison term for possession of pornography involving children under 14 years is two years.
Production and distribution of child pornography is punishable by up to 10 years in jail.