Fourteen suspected paedophiles were arrested in Northern Ireland as part of the biggest ever UK crackdown on obscene images of children, it has emerged.
Doctors, teachers and former police officers were among 660 people arrested across the UK for downloading and sharing the sickening pictures.
The PSNI has revealed it carried out 15 searches and made 14 arrests as part of the unprecedented swoop, headed by the National Crime Agency (NCA).
Two children were identified in Northern Ireland to be "at potential risk" and have been protected through social services.
The nationwide operation has already led to charges for serious sexual assault.
A PSNI statement said: "The aim of this operation is to protect children who are victims of, or might be at risk of, sexual exploitation.
"The targets were people accessing indecent images of children online and the majority of these people were not yet known to police – they are now, and they will stay in our sights."
Those arrested included a doctor who had access to more than one million depraved pictures, was found to have met up with boys and kept sex aids and rope in the boot of his car.
Scout leaders and care workers were also among the huge number of people held across England, Wales, Scotland and Northern Ireland, and the vast majority had never before aroused suspicion.
The massive investigation, involving all 45 British police forces, led to 431 children who were were in the "care, custody or control" of the suspects being "safeguarded", including 127 who were identified as being at serious risk of harm.
Those arrested had used the internet or the so-called "dark web" - internet content that is not listed for access by normal search engines.
The PSNI said: "A child is victimised not only when they are abused and an image is taken but they are re-victimised every time that image is viewed by someone.
"We have identified that many offenders who start by accessing indecent images online go on to abuse children directly so the operation is not only about detecting people who have already offended – it is about reducing the risk of serious harm to children."
'No hiding place'
Detectives are not revealing the precise tactics used as the operation as it is still ongoing, but warned offenders that the internet is "not a safe hiding place".
"We will continue to use a range of investigative techniques targeting all forms of abuse to protect children and vulnerable people and bring offenders to justice," the statement added.
"Officers working in the PSNI and Child Exploitation and Online Protection (CEOP) routinely work side by side with professionals from the wider child protection community and industry to identify the main threats to children and coordinate activity against these threats to bring offenders to account.
"They routinely police the internet to protect children from harm online and offline and and pursue those who sexually exploit and abuse children, prevent people becoming involved in child sexual exploitation, protect children from becoming victims of sexual exploitation and sexual abuse, and prepare interventions to reduce the impact of child sexual exploitation and abuse through safeguarding and child protection work."
National Crime Agency deputy director general Phil Gormley said he was "profoundly disappointed" that so many suspects had been arrested over this type of crime.
He said: "The alternative is not to look under the stone, and we cannot afford not to look under this stone.
"There are very significant volumes of people viewing this material in this country and abroad. We are going to need to understand as a society how we are going to confront this issue.
"We are not going to be able to arrest our way our of it. The numbers are significant, the volumes are huge."
In previous child abuse cases officers have gone undercover and posed as potential victims to lull sex offenders into showing their true colours.
There were only 39 registered sex offenders among those arrested, with the majority able to avoid detection until now.
One of the suspects said he had been viewing images of child abuse for 30 years and had repeatedly travelled to south east Asia as a sex tourist.
When asked how hundreds of sex offenders had escaped detection until now, Mr Gormley said: "It's a bit like a drugs problem. You need to look for it if you're going to find it. People are unlikely to report this type of crime, you're not going to have witnesses to it in the way that traditional crime types will."
Two years ago the NCA estimated that 50,000 people in the UK were involved in sharing child abuse images online, and in the past 20 years the number of images available has soared from an estimated 10,000 to tens of millions.
Mr Gormley went on: "I am pretty appalled about what it says about human nature. Which is why we need to think very carefully about what this means and how we approach this type of offending behaviour, and the propensity of quite large numbers of people to view this material."
So far officers have searched 833 properties and examined 9,172 computers, phones and hard drives.
The NCA said it built up "intelligence packages" on suspects and sent them to police forces across Britain before arrests were made.
Claire Lilley, head of online safety at the NSPCC, said: "Direct action like this sends a strong message to those who subject children to harrowing sexual assaults that they can and will be traced and prosecuted.
"But law enforcement agencies alone cannot deal with the vast problem of illegal images which continue to flood the market. Industry has to find inventive ways of blocking the flow of such horrendous pictures which are only produced through the suffering of defenceless children - many of who are not even old enough to go to school.
"So while this operation must be rightly applauded we should view it as yet another warning sign that far more needs to be done if we are to stem the sordid trade in these images, which are often used by those who go on to abuse children."
Additional reporting by PA