Pope Francis accused victims of Chile's most notorious pedophile of slander Thursday, an astonishing end to a visit meant to help heal the wounds of a sex abuse scandal that has cost the Catholic Church its credibility in the country.

Francis said that until he sees proof that Bishop Juan Barros was complicit in covering up the sex crimes of the Rev. Fernando Karadima, such accusations against Barros are "all calumny."

The Pope's remarks drew shock from Chileans and immediate rebuke from victims and their advocates. They noted the accusers were deemed credible enough by the Vatican that it sentenced Karadima to a lifetime of "penance and prayer" for his crimes in 2011. A Chilean judge also found the victims to be credible, saying that while she had to drop criminal charges against Karadima because too much time had passed, proof of his crimes wasn't lacking.

"As if I could have taken a selfie or a photo while Karadima abused me and others and Juan Barros stood by watching it all," tweeted Barros's most vocal accuser, Juan Carlos Cruz. "These people are truly crazy, and the pontiff talks about atonement to the victims. Nothing has changed, and his plea for forgiveness is empty."

Juan Carlos Cruz says he and another teen boy were sexually molested by Rev. Fernando Karadima. (Matt Rourke/Associated Press)

The Karadima scandal dominated Francis's visit to Chile and the overall issue of sex abuse and church cover-up was likely to factor into his three-day trip to Peru that began late Thursday.

Karadima's victims reported to church authorities as early as 2002 that he would kiss and fondle them in the swank Santiago parish he ran, but officials refused to believe them. Only when the victims went public with their accusations in 2010 did the Vatican launch an investigation that led to Karadima being removed from ministry.

The emeritus archbishop of Santiago subsequently apologized for having refused to believe the victims from the start.

Francis reopened the wounds of the scandal in 2015 when he named Barros, a protege of Karadima, as bishop of the southern diocese of Osorno. Karadima's victims say Barros knew of the abuse, having seen it, but did nothing. Barros has denied the allegations.

'It's all calumny. Is that clear?'

His appointment outraged Chileans, badly divided the Osorno diocese and further undermined the church's already shaky credibility in the country.

Francis had sought to heal the wounds by meeting this week with abuse victims and begging forgiveness for the crimes of church pastors. But on Thursday, he struck a defiant tone when asked by a Chilean journalist about Barros.

Pope Francis has again defended the bishop of Osorno, Juan Barros, seen here on Jan. 18 at an open-air mass celebrated the Pope, against accusations that Barros covered up for Chile's most notorious pedophile priest. (Vincezo Pinto/AFP/Getty Images)

"The day they bring me proof against Bishop Barros, I'll speak," Francis said. "There is not one shred of proof against him. It's all calumny. Is that clear?"

Francis had defended the appointment before, calling the Osorno controversy "stupid" and the result of a campaign mounted by leftists. But The Associated Press reported last week that the Vatican was so worried about the fallout from the Karadima affair that it was prepared in 2014 to ask Barros and two other Karadima-trained bishops to resign and go on a yearlong sabbatical.

Bishop not recognized by many priests

According to a Jan. 31, 2015, letter obtained by AP from Francis to the executive committee of the Chilean bishops' conference, the plan fell apart and Barros was sent to Osorno.

Juan Carlos Claret, spokesperson for a group of Osorno lay Catholics who have mounted a three-year campaign against Barros, questioned why Francis was now accusing the victims of slandering Barros when the Vatican was so convinced of their claims that it planned to remove him in 2014.

Police detain a protester dressed as a priest as Pope Francis arrives in Santiago, Chile. (Carlos Vera/Reuters)

"Isn't the pastoral problem that we're living [in Osorno] enough to get rid of him?" Claret asked.

The reference was to the fact that — guilty or not — Barros has been unable to do his job because so many Osorno Catholics and priests don't recognize him as their bishop. They staged an unprecedented protest during his 2015 installation ceremony and have protested his presence ever since.

'He has just turned back the clock'

Anne Barrett Doyle, of the online database BishopAccountability.org, said it was "sad and wrong" for the Pope to discredit the victims since "the burden of proof here rests with the church, not the victims — and especially not with victims whose veracity has already been affirmed."

"He has just turned back the clock to the darkest days of this crisis," she said in a statement. "Who knows how many victims now will decide to stay hidden, for fear they will not be believed?"

Pope Francis smiles as he walks to the altar at Lobitos Beach in Chile. He is now in Peru on the last leg of his South American trip. (AFP/Getty Images)

Indeed, Catholic officials for years accused victims of slandering and attacking the church with their claims. But up until Francis's words Thursday, many in the church and Vatican had come to reluctantly acknowledge that victims usually told the truth and that the church for decades had wrongly sought to protect its own.

German Silva, a political scientist at Santiago's Universidad Mayor, said the Pope's comments were a "tremendous error" that will reverberate in Chile and beyond.

Scandal strongly affected Chileans

Patricio Navia, political science professor at Diego Portales University in Santiago, said Francis had gone much further than Chilean bishops in acknowledging the sexual abuse scandal, which many Chileans appreciated.

"Then right before leaving, Francis turns around and says: `By the way, I don't think Barros is guilty. Show me some proof,"' Navia said, adding that the comment will probably erase any good will the Pope had won over the issue.

Navia said the Karadima scandal had radically changed how Chileans view the church.

"In the typical Chilean family, parents [now] think twice before sending their kids to Catholic school because you never know what is going to happen," Navia said.