About 2,000 demonstrators in Belgium on Sunday protested the possible early release from prison of the ex-wife of a pedophile, who was an accomplice in his abuse and murder of young girls.

The protesters in Brussels braved some of the year's hottest weather of 35 C (95 F) to show their displeasure with the possibility that Michelle Martin, former wife of child rapist Marc Dutroux, could move to a convent after her conditional release.

The Dutroux case is one of the most sensational in Belgium's recent history. Dutroux, now 55, is serving a life term for kidnapping, torturing and abusing six girls in 1995 and 1996, and murdering four of them.

Martin, who was sentenced to 30 years in prison for helping her husband, has served 16 years of her term, but could be released within weeks.

"Thirty years is 30 years," some of the protesters were shouting.

'What crime do you have to commit to serve a full term?'—Paul Marchal, father of Dutroux's victim

"What crime do you have to commit to serve a full term," said Paul Marchal, whose daughter was a victim of Dutroux. He demanded that victims and their survivors have a bigger role in the decision on conditional early release.

"It is very important that the victims can have a say in the cases," Marchal said.

Martin, 52, allowed two 8-year-old girls imprisoned in a decrepit basement to die of starvation while Dutroux spent four months in jail for theft.

A woman wearing a costume representing Justice takes part in a demonstration in Brussels, Sunday. A woman wearing a costume representing Justice takes part in a demonstration in Brussels, Sunday. (Sebastien Pirlet/Reuters )

The protesters said Martin should not be free to come and go from the convent in Malonne, 45 miles (75 kilometres) southeast of Brussels.

"We are marching for our grandson who is 2 and half years old and we want him to live in a country where there is justice," said Murielle Bontemps, a grandmother from Liege, 100 kilometres (60 miles) east of Brussels. "That he will not fear going out to play out with his friends, and that we won't fear that he'll get kidnapped, because what we are doing now is we set predators free."