Images of children as young as two have been uncovered in a series of police raids to trap traders in Internet child pornography.
Police have arrested 60 people across the north of England as part of a long-running investigation linked to the use of an American child porn website.
About 200 officers were involved in Operation Ore, which included searches of more than 50 homes and the seizure of hard drives from more than 100 computers.
A total of 56 men and four women were arrested and released on bail pending further enquiries. No further action is being taken against one further man who was arrested.
Officers also seized thousands of CDs, floppy disks and DVDs, which are being analysed by the Northumbria Police computer crime unit.
Police say one man had hidden more than 12,000 indecent images of children inside an off-the-shelf computer game stored on his computer.
Detective Chief Inspector Michael Jones said the images showed children as young as two, sometimes alone, with other children, or with adults.
Many of the children appeared to be from the Far East and eastern Europe, but also included others who could be from the UK.
He said: "Every time someone looks at an image of a child being sexually abused they are paying to watch a crime being committed.
"This isn't about someone indulging in their private fantasies in the privacy of their own home without affecting anyone else."
He said the children were "real victims" who were being exploited and damaged.
"This operation proves that no matter how hard someone tries to hide illegal material on a computer, we have ways of finding it.
"They might be able to hide it from their wives or partners, but they can't hide it from the police."
In June Northumbria Police officers began analysing data which showed that British citizens had visited a US-based website selling access to sites that held images of the sexual abuse of children.
Six weeks ago, after checking addresses and gathering further intelligence, they began the series of arrests across Tyne and Wear and Northumberland.
Mr Jones added: "Close co-operation with Internet service providers and other law enforcement agencies is helping to reduce the ease with which paedophiles can operate online to hide their criminal activities.
"Using the sophisticated technology that is now available to us, along with traditional detective and analytical work, we can now identify these people, who presumably thought that their activities could remain undetected."
Those found guilty of possessing indecent photographs of children can be jailed for up to five years, while making or distributing images both have maximum sentences of 10 years.
Anyone convicted is automatically placed on the Sex Offenders Register.
Although access to the US website has been blocked since 1999, computers seized in the North East show that suspects have found other sources of child abuse imagery.
Mr Jones added: "Because of the detailed information which had to be keyed in before people could access the websites, it is extremely unlikely that anyone accessed any of the websites accidentally.
"However, there is nothing to suggest that the people we have arrested are linked in any way other than that they used the same websites.
"There is no evidence of any paedophile ring operating in this area as a result of this access."
In May, two men were arrested in the Northumbria Police area.
Although no evidence was found in one of the searches the other revealed that a Newcastle man had saved 17,000 pornographic images of children and spent £600 on his credit card to access the sites where the picture were held.
He has been charged and the case is progressing through the courts.