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Pope Francis celebrates a Mass in Sibari, southern Italy, Saturday, June 21, 2014. Pope Francis paid a one day visit to Castrovillari, Sibari, and Cassano allo Jonio, in the Calabria region of Italy. Pope Francis comforted the imprisoned father of a slain toddler during a visit Saturday to a southern Italian region infested by one of the world's most powerful crime syndicates. During his one-day pilgrimage to Calabria, Francis met separately with the father and two grandmothers of Coco' Campolongo in the courtyard of a prison in the town of Castrovillari. (AP Photo/Alessandra Tarantino)

VATICAN CITY (AP) — Pope Francis is urging Christians to work together to abolish every form of torture, condemning the practice as a grave sin.

Francis told the public in St. Peter's Square Sunday he wanted to reiterate his "firm condemnation of every kind of torture." He sought united efforts to work for torture's end and to support victims and their families.

Francis said it was a "mortal sin, a very grave sin, to torture people" and noted that Thursday marks the United Nation's day for torture victims.

Torture was a powerful tool of the military regime ruling his native Argentina from 1976 till 1983. The local church hierarchy then openly sided with the junta.

Francis has been credited with saving lives of political dissidents while a Jesuit priest in Argentina.