We can detect them and recover images they have accessed - but we are really doing it to explore their lives and see if they are doing it to real kids

Detective Inspector Terry Jones

A man aged 42 from Merthyr Tydfil was still being questioned late on Wednesday.

A 29-year-old man from the Rhondda Cynon Taff area was also being held.

A 17-year-old from Caerphilly was later released on bail while two men from the Carmarthen were also released on bail while the police enquiry continues.

Dyfed-Powys Police said no further action was being taken against the other two men arrested in their area.

A spokesman said the four men arrested in the Dyfed-Powys force area were aged between 19 and 60.

Operation Magenta, targeted internet users who visited online chatrooms to exchange shocking images of child abuse.

Police used specially-developed software to track them through cyberspace and into the real world .

Police said they believed many may be directly involved in child abuse

Altogether 75 addresses in Wales, England, Scotland, and Northern Ireland were raided simultaneously at 0700 BST on Thursday.

It was the culmination of a six-month investigation, under the Protection of Children Act, led by officers from Hertfordshire Constabulary and Greater Manchester Police.

Detective Inspector Terry Jones, head of Greater Manchester Police's abusive images unit, said of the people they were targeting: "We can detect them and recover images they have accessed - but we are really doing it to explore their lives and see if they are doing it to real kids."

"We will not be leaving those premises until we are satisfied those children are safe," said Detective Inspector Keith Tilley, head of Hertfordshire Constabulary's child protection and investigation unit.

Police said they believed many of those involved in swapping images may also be directly responsible for child abuse.

Detectives were able to make use of specialist equipment to trace computers being used by people entering the chat rooms anonymously.

The maximum sentence for downloading child porn photographs is 10 years in prison.

Some business addresses were among the 75 searched by police in Operation Magenta.

Officers were making inquiries to establish who was using particular terminals at certain times.