An alleged paedophile who posted around 200 photos of himself on the internet has been unmasked after computer experts reversed the digital process he used to hide his identity.

Interpol is now making a rare public worldwide request for assistance in identifying the man.

The original photographs had been digitally altered with a swirling pattern to disguise the man's face.

But computer specialists from the Bundeskriminalamt federal police agency in Germany, working with Interpol's Trafficking in Human Beings unit, have been able to reverse the process to produce an identifiable picture.

"For years images of this man sexually abusing children have been circulating on the internet," said Ronald K. Noble, secretary general at Interpol.

"We have tried all other means to identify and to bring him to justice, but we are now convinced that, without the public's help, this sexual predator could continue to rape and sexually abuse young children whose ages appear to range from six to early teens.

"We have very good reason to believe that he travels the world in order to sexually abuse and exploit vulnerable children and, as an 186-member country police organisation, Interpol is uniquely positioned to co-ordinate this global effort to identify and bring him to justice."

The search for the individual has been codenamed 'Vico' after analysis of the photographs featuring 12 different young boys established that the pictures were taken in Vietnam and Cambodia in 2002 and 2003.

Kristin Kvigne, assistant director of Interpol's Trafficking in Human Beings Unit, said: "The decision to make public this man's picture was not taken lightly.

"We are certainly not encouraging members of the public to take any direct action themselves, particularly since any positive identification would need to be confirmed by law enforcement authorities.

"But if anyone recognises this person, or has any information that could help investigators, please contact the police or Interpol National Central Bureau in your country."

Interpol received over 200 messages within 12 hours of the appeal being made.

Anders Persson, a police officer in charge of Interpol's child abuse images team, said that it has had "a lot of responses from all over the world". These include messages containing detailed information such as names and addresses.