A Madonna statue is carried during religious procession in Oppido Mamertina, Calabria region, Southern Italy. (AP Photo/Toni Condello)

Rome - Anti-mafia police launched an investigation on Monday after a religious procession in a southern Italian town detoured to pay tribute to a local mobster, in apparent defiance of Pope Francis.

The procession in Oppido Mamertina, a Calabrian town considered a stronghold of the 'Ndrangheta crime syndicate, on Wednesday changed course to visit where mob boss Giuseppe Mazzagatti is being held under house arrest.

Those carrying a statue of the Madonna bent down to make the effigy bow to the building, Italian media reported.

The Argentine pontiff visited Calabria last month, where he launched a scathing attack on the mafia for its “adoration of evil” and excommunicated its members from the Catholic Church.

Police said Monday they were investigating possible collusion between the leaders of the procession and Mazzagatti, 82, who is serving a life sentence under house arrest for health reasons.

Prosecutors are looking at video footage taken by local police during the procession.

“Whoever made the Madonna bow has committed a double sin,” Nunzio Galantino, head of the Italian episcopal conference, told the Corriere della Sera daily.

“It twisted the sense of the procession,” he said. “It's absurd.”

“The Madonna can bow to poverty, to those in need, in front of a sincere conversion, but not in subjugation to a delinquent.”

Francis's words during a trip to the hometown of a toddler killed by the mafia appear to also have sparked rebellion among those serving time for mafia-related crimes.

People who are excommunicated are expelled from the Church, unless they repent, and are considered to be condemned to hell in the afterlife.

Bishop Giancarlo Bregantini told Vatican Radio on Sunday that around 200 prisoners held in maximum security in Larino jail had threatened to boycott mass after their excommunication, saying they felt cast out by the Church.

But Roberto Saviano, who has lived under police protection since infiltrating the Naples mafia, said it was “not a protest by (mafia) members against a Church, which has abandoned them”.

“It is a declaration of obedience to the 'Ndrangheta, a confirmation of the promise of fidelity to the saint,” he told La Repubblica daily, explaining that new mobsters swear allegiance to Saint Michael the Archangel, who is regarded by the crime group as their patron saint.

The 'Ndrangheta plays a leading role in the global cocaine trade and its bastion, the poor Calabria region, is a major transit point for drug shipments from Latin America to the rest of Europe.

The mafia has benefitted in the past from historic ties to the Church, with dons claiming to be God-fearing Catholics and priests turning a blind eye to crimes.