Michelle Martin, 51, has served only half her 30-year jail term for complicity in the imprisonment and murder of the young victims of her serial killer husband Marc Dutroux.
Families of Dutroux’s victims have said the Belgian court in Mons is ‘allowing a monster out into society’ by ordering her release.
She will spend her ten-year probation period in an overseas convent - at her own request.
Dutroux was arrested in 1996 and jailed for life in June 2004 for the kidnapping, rape and torture of six young girls in the mid-1990s, four of whom died.
Martin was also arrested in 1996 and later found guilty of helping Dutroux imprison his victims prisoner.
She was also convicted of complicity in the death of two of the small girls, found starved to death in a cellar in the southern city of Charleroi.
The traumatic case is still fresh in the minds of many in Belgium, which is also reeling from a Catholic church child abuse scandal involving more than 500 victims.
Under Belgian law, convicts can appeal for early release after serving a third of their sentence.
Prosecutors are planning to appeal against the controversial decision to free Martin at a higher court today.
She will remain behind bars until a final decision is made.
Outraged Jean-Denis Lejeune, mother of Julie Lejeune, one of the two eight-year-olds found in Dutroux’s cellar, said: 'She murdered my daughter, 15 years seems light.
'I cannot believe we are allowing a monster out into society.' Read More