Pope Francis told Chile's priests Tuesday that sexual abuse of children not only has caused pain to the victims but also to the priests who have been held collectively responsible for the crimes of a few.

At a meeting in Santiago's cathedral, Francis urged priests and nuns to have the strength to ask for forgiveness for abuse and the "clear-sightedness to call reality by its name."

Francis denounced the "weeds of evil" that had sprung up as a result of the scandal, and said he appreciated how the church was responding to it. He said the scandal was particularly painful "because of the harm and sufferings of the victims and their families, who saw the trust they had placed in the church's ministers betrayed.

"Pain too for the suffering of ecclesial communities, and pain for you brothers and sisters, who after working so hard, have seen the harm that has led to suspicion and questioning; in some or many of you this has been a source of doubt, fear or lack of confidence."

He said at times, some had even been insulted in the metro and that by wearing clerical attire they had "paid a heavy price." But he urged them to press on.

Earlier Tuesday Francis begged for forgiveness for the "irreparable damage" done to children who were raped and molested by priests, opening his visit to Chile by diving head-first into a scandal that has greatly hurt the Catholic Church's credibility in the country and cast a cloud over his visit.

Francis faced controversy on another front as well: Overnight, three more Catholic churches were torched, including one burned to the ground in the southern Araucania region where Francis will visit on Wednesday to meet with Indigenous people.

While not causing any injuries, the nine church firebombings in the past few days have marked an unprecedented level of protest against history's first Latin American Pope on his home turf.

In Santiago, though, an estimated 400,000 jubilant Chileans turned out in droves for his first public mass, a massive gathering in the capital's O'Higgins park where St. John Paul II celebrated mass three decades ago. Before the service began, Francis took a long, looping ride in his Popemobile through the grounds to greet well-wishers, some of whom had camped out overnight to secure a spot.

A man is arrested during a protest against Pope Francis in Santiago on Tuesday. The pontiff is visiting Chile, where the Vatican's handling of sex abuse cases has fuelled bitter criticism. (Victor R. Caivano/Associated Press)

In his first event of the day, Francis met privately with Chilean President Michelle Bachelet and addressed lawmakers, judges and other authorities at La Moneda palace. They interrupted him with applause when he said he felt "bound to express my pain and shame" that some of Chile's pastors had sexually abused children in their care.

"I am one with my brother bishops, for it is right to ask forgiveness and make every effort to support the victims, even as we commit ourselves to ensuring that such things do not happen again," he said.

Francis didn't refer by name to Chile's most notorious pedophile priest, the Rev. Fernando Karadima, who was sanctioned in 2011 by the Vatican to a lifetime of "penance and prayer" for sexually molesting minors. Nor did he refer to the fact that the emeritus archbishop of Santiago, a top papal adviser, has acknowledged he knew of complaints against Karadima but didn't remove him from ministry.

Karadima had been a politically connected, charismatic and powerful priest who ministered to a wealthy Santiago community, and produced dozens of priestly vocations and five bishops. Victims went public with their accusations in 2010, after complaining for years to church authorities that Karadima would kiss and fondle them when they were teenagers.

While the scandal rocked the church, many Chileans are still furious over Francis's subsequent decision, in 2015, to appoint a Karadima protege as bishop of the southern city of Osorno. Bishop Juan Barros has denied knowing about Karadima's abuse, but many Chileans don't believe him and his appointment has badly split the diocese.

Barros attended a Mass celebrated by Francis Tuesday in Chile's capital of Santiago. Upon exciting, Barros told local media that, in his words, "Many lies have been made about me."

Barros again said he did not witness any abuse by Karadima.

Nearly 80 priests accused

Anne Barrett Doyle, of the online abuse database BishopAccountability.org, praised Francis for opening his visit with the apology, but said Chileans expect him to take action against complicit church leaders.

"This is a crucial opportunity for Francis: With luck, he will not make the mistake of his brother bishops in underestimating the savviness and moral outrage of the Chilean people," said Barrett Doyle, who last week released research showing nearly 80 Chilean priests have been credibly accused or convicted of abuse.

From a balcony, protesters dressed as clerics gesture and display a banner saying: 'I love pedophilia.' (Victor R. Caivano/Associated Press)

The Karadima scandal and a long coverup has caused a crisis for the church in Chile, with a recent Latinbarometro survey saying the case was responsible for a significant drop in the number of Chileans who call themselves Catholic, as well as a fall in confidence in the church as an institution.

That distrust extends to Francis, who is making his first visit as Pope to this country of 17 million. The Argentine Pope is nearly a native son, having studied in Chile during his Jesuit novitiate and he knows the country well, but Chileans give him the lowest approval rating among the 18 Latin American nations in the survey.

"People are leaving the church because they don't find a protective space there," said Juan Carlos Claret, spokesperson for a group of church members in Osorno that has opposed Barros's appointment as bishop. "The pastors are eating the flock."

Tear gas, water cannons at protest

At a protest Tuesday near O'Higgins park where Francis celebrated mass, police fired tear gas and water cannons before detaining several dozen demonstrators, according to an Associated Press photographer at the scene. Protesters carried signs with messages reading "Burn, Pope!" and "We don't care about the Pope!"

Other groups also called for demonstrations against the pontiff.

Victor Hugo Robles, an activist in Chile's lesbian and gay community, said the Vatican tries to paint an image of the Pope as being close to the people, particularly those with the most needs.

"We are the ones who need help," said Robles. "Gay people, people living with AIDS. When it comes to those things, the church has an attitude of intolerance, of disgust."

Felipe Morales, from a group called the Workers' Socialist Front, said many were unhappy with the Pope and the church's historical influence in Chile. They planned to protest outside while Francis celebrated mass.

"The role of the church has been nefarious," said Morales. "Sex abuse cases have been covered up and people are unhappy with many other issues."

Pope Francis arrives Tuesday at O'Higgins Park in Santiago. An estimated 400,000 jubilant Chileans turned out in droves for his first public mass. (Natacha Pisarenko/Associated Press)

The Pope will try to inject new energy into the church during his visit, which includes sessions with migrants, members of Chile's Mapuche Indigenous group and victims of the 1973-1990 military dictatorship. It remains to be seen if he will meet with sex abuse survivors. A meeting wasn't on the agenda, but such encounters never are.