Paris ? He apparently traveled the world sexually abusing young boys, but remained unidentifiable – until now.

Police in Europe have unscrambled digitally altered images found on the Internet to reveal the face of a man shown abusing boys in Vietnam and Cambodia.

Interpol released four reconstructed photos of the suspected pedophile on Monday in an unprecedented public appeal for help, hoping that someone, somewhere, will recognize the man whose identity and nationality remain a mystery.

The response has been encouraging: about 200 messages in just over 12 hours, Interpol said.

But the decision to unmask him is not without risk: Tipping criminals off to the techniques that police have at their disposal could also prompt them to better hide their identities.

Interpol said 12 boys, apparently ranging in age from 6 to early teens, appeared in about 200 photographs posted on the Internet. But the face of the man inflicting the abuse was disguised in a digital whirl.

Using techniques that neither they nor Interpol would discuss, German police produced identifiable images of the man from the original pictures. The reconstructed photos showed a white man who looked to be in his 30s, with uncombed short brown hair. One showed him wearing glasses, in another he smiled, and another showed that he has a hairy chest. Interpol posted the images on its Web site.

The photos must date from before December 2004, when they were found on the Internet.