"With regard to the recent media frenzy, Christ is the Answer does not currently, nor will it, host any persons coming from Belgium," the group, based on the outskirts of Florence, said in a note on its website.
"This decision was taken some time ago," it said.
Michelle Martin was freed on parole in 2012 after 16 years in prison on condition that she move into a Belgian convent near the central city of Namur.
But the nuns are now moving to Brussels and do not want her to come with them.
Martin – whose move into the convent provoked widespread outrage – has asked the authorities for permission to seek refuge elsewhere.
Belgian regional media group Sudpresse said Martin was cleared on January 2nd to go to Italy for a week, hoping to find a welcome in the Christ is the Answer community which had initially responded favourably to the request.
Dutroux was jailed for life in 2004 for the kidnap and rape between 1995 and 1996 of six girls, and the murder of four of his victims, in one of the darkest episodes in Belgium's criminal history.
Martin, a former schoolteacher who was detained in 1996, was sentenced too in 2004 for helping him hold the girls captive and for complicity in the deaths of two who were found starved to death in a locked cellar.
Martin married Dutroux in 1983 and had three children with him before they divorced in 2003.