BRUSSELS: Belgian Prime Minister Elio Di Rupo pledged Saturday to toughen parole rules after a massive outcry over the release of the accomplice and ex-wife of pedophile serial killer Marc Dutroux.

Michelle Martin, a former school teacher branded Belgium's "most hated woman" for allowing two children to starve to death, won parole Tuesday midway through her 30-year jail term, on condition that she move into a convent.

Di Rupo said the government was preparing to tighten regulations governing parole by ensuring that offenders serve at least three-quarters of a 30-year sentence before they get the chance of conditional release.

"Our aim must be no to impunity. We must embark on a series of reforms in the police and the judicial system," he said in an interview with several Belgian newspapers.

Di Rupo also said Belgium would hire at least another 1,400 police officers, after the Dutroux affair exposed major failings in the police and judiciary. Dutroux was finally jailed for life in 2004 for the kidnap and rape between 1995 and 1996 of six young and teenage girls, and the murder of four of his victims, in one of the darkest episodes in Belgium.

Martin, 52, who was detained in 1996, was also sentenced in 2004 for helping him hold the girls captive and for complicity in the deaths of two of them found starved to death in a locked cellar.

There have been calls on the Internet for demonstrations Saturday at the convent in the village of Maronne in southern Belgium where Martin is now living.

Martin married Dutroux in 1983 and had three children by him before they divorced in 2003. Both had served time in the early years of their marriage for previous kidnappings.