PARIS -- It is a horror story told many times in many places: a convicted child kidnapper and rapist serves time in prison. He is let off early for good behavior. The pedophile, unable or unwilling to control his demons, strikes again.

Marc Dutroux, 39, an unemployed Belgian electrician who was previously convicted of abusing children, has followed the pattern to the letter. In recent days, he has released two pallid young girls, aged 12 and 14, who were sexually abused while locked in a hidden dungeon in one of his several homes. Then he led police to the secret graves of two 8-year-old girls he said had starved to death while in his home.

After pornographic films and photographs were found in another of the houses he owns in different towns in Belgium, the police said he confessed to his role in the kidnapping last year of two teen-agers, who were 17 and 19 at the time. The two girls are still missing, but authorities say it is possible that they are alive.

As the story unfolded in ever more gruesome detail this week, the people of Belgium, many of whom were familiar with the faces of the victims from the ubiquitous "missing" posters, have begun circulating petitions about measures for dealing with sex offenders and calling for restoring the death penalty.

The case has commanded front-page attention across Europe, where it has revived the debate over how to punish or control known offenders, and what degree of freedom they should have after serving sentences.

The issue of whether to notify a community that a convicted sex offender released from prison is in the area has been the subject of legislation in the United States.

The fate of the six girls, and of six other children who are still missing, has engendered a sense of national mourning, with television images from across the country Wednesday showing cars driving around with black ribbons and demonstrators carrying signs saying, "To death."

In Sars-la-Buissiere, a small village near Charleroi, in the south of Belgium, the home of the two dead girls and the site of one of Dutroux's houses, thousands have already filed past the two white coffins of the little girls, whose bodies were exhumed from their clandestine grave but are to be formally buried on Thursday.

Some human rights groups argue that the industry of sexually exploiting children is expanding, made easier through videos, computer links and cheap travel to countries where poor children can be bought with relative impunity. The police now suspect that Dutroux may have profited from selling both children and child pornography.

The parents of the dead girls are also demanding access to police files and explanations of how the police could overlook important leads, like the fact that Dutroux, his wife and three children were apparently living on unemployment checks, yet he owned at least six houses and as many cars.

Several European countries, including France and Germany, have hardened their sentences for child abusers in recent years, while some, including the Netherlands, insist on supervision and counseling after a convict's release and in some cases resort to chemical "castration," administering hormones to inhibit the abuser's libido.

In Belgium, however, laws are more lenient. Dutroux was sentenced in 1989 to 13 years in prison on multiple counts of rape and child abuse. But he was released after three years for good behavior, even though his own mother warned of the risks of recidivism.

Belgians are also venting their anger against what they see as police bungling. Belgian newspapers today published leaked police documents showing that the police had been receiving tipoffs from an informer since 1993, warning that Dutroux was "building cells" to hold kidnapped children.

The police this year made two visits to the house where the two girls were held captive and said they believed Dutroux when he said the voices they heard were those of his own children, the documents said.

In the grave in the Dutroux backyard, the police also found the body of Bernard Weinstein, an associate of Dutroux's. Dutroux told the police that he killed Weinstein in a rage because he had given Weinstein money to feed the two 8-year-old prisoners while he served a brief sentence in jail. Dutroux said that the girls died of starvation.

Beside Dutroux, three other adults, including his second wife, Michelle Martin, have been arrested as accomplices in the abduction and illegal imprisonment of children.

The police are now hunting for the two teen-agers, whom Dutroux said he and an associate kidnapped last year in the coastal resort of Ostend. Belgium's attorney general said Wednesday that there was reason to believe that they might be alive and in the hands of a prostitution ring elsewhere in Europe. He said that the police were working through Interpol and through authorities in nearby countries, including the Czech Republic and Germany.

Copyright 1996 The New York Times