Pope Francis leads a mass on New Year's Day at Saint Peter's Basilica at the Vatican January 1, 2017. REUTERS/Remo Casilli

VATICAN CITY (Reuters) - Pope Francis appealed on Wednesday for prisoners around the world to be treated humanely following the deadliest jail riot in Brazil for two decades, in which 56 inmates died.

Violence erupted between rival drug gangs on Sunday in a prison in the jungle city of Manaus. Some inmates were decapitated and their bodies tossed over a wall of the penitentiary, which houses more than three times its capacity.

“I express my pain and concern for what happened,” Pope Francis said at his weekly general audience in the Vatican.

“I pray for those who have died and their families and for all prisoners in that prison and those who work there. I renew my appeal that prisons should be places of re-education and re-integration into the community, and the conditions for prisoners should be fitting for human beings,” he said.

The Argentinian-born pope often visits prisons on his foreign trips and recently held a Mass for some 1,000 inmates who were briefly allowed out of prison to attend the service in St. Peter’s Basilica.