Vatican City -- Pope Francis warned bishops and religious superiors summoned Thursday to a landmark sex abuse prevention summit that the Catholic faithful are demanding not only condemnation of the crimes but concrete action to respond to the scandal.

Francis opened the four-day summit by telling the Catholic hierarchy that their own responsibility to deal effectively with the crimes of priests who rape and molest children weighed on the proceedings.

He told the 190 leaders of bishops conferences and religious orders to "listen to the cry of the young who want justice" and seize the opportunity to "transform this evil into a chance for understanding and purification."

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"The holy people of God are watching and expect not just simple and obvious condemnations, but efficient and concrete measures to be established," he warned.

Pope Francis prays during the opening of a global child protection summit for reflections on the sex abuse crisis within the Catholic Church, on February 21, 2019 at the Vatican Vincenzo Pinto / AFP/Getty Images

On the eve of the summit, the pope met with an abuse survivor from Poland, reports CBS News correspondent Seth Doane.

Notably, victims were not inside the auditorium Thursday morning, though their videotaped testimony was played.

More than 30 years after the scandal first erupted in Ireland and Australia and 20 years after it hit the U.S., bishops and superiors in many parts of Europe, Latin America, Africa and Asia either deny that clergy sex abuse exists in their regions or downplay the problem.

Francis, the first Latin American pope, called the summit after botching a well-known sex abuse cover-up case in Chile last year. Realizing he had erred, he has vowed to chart a new course and is bringing the rest of the church leadership along with him.

The summit is meant as a tutorial for church leaders to learn the importance of preventing sex abuse in their churches, tending to victims and investigating the crimes when they occur.

In the keynote speech, Manila Cardinal Luis Tagle choked up several times as told the bishops that the wounds the scandal has caused among the faithful recalled the wounds of Christ on the cross. He demanded they longer run in fear or turn a blind eye to the harm caused by clergy sex abuse and their own inaction to halt the problem.

"Faith that would like to close its eyes to peoples' suffering is just an illusion," he said.

Abuse survivors have turned out in droves to demand accountability and transparency from church leaders, saying the time of cover-up is over.

Phil Saviano, who helped expose the U.S. scandal two decades ago, demanded the Vatican release the names of abusers and their files.

Two men talk in front of Saint Peter's Basilica ahead of four-day meeting on global sexual abuse crisis, held by Pope Francis, at the Vatican, on February 21, 2019 REMO CASILLI / REUTERS

"Do it to break the code of silence," he told the organizing committee on the eve of the summit. "Do it out of respect for the victims of these men, and do it to help prevent these creeps from abusing any more children."

The pontiff upset at least one man who attended an unprecedented meeting Wednesday between bishops and survivors of alleged clergy sexual abuse.

Shaun Dougherty, of Pennsylvania, told CBS News' Nikki Battiste he'd been waiting years for that moment and hoped the pope himself would be at the session. He wasn't.

"I'm not surprised, I'm aggravated. This is the CEO of the Roman Catholic Church," Dougherty said. "We came to his house to meet with him about his abusive priests ... and he wasn't there. He delegated."

The Vatican isn't expecting any miracles or even a final document to come out of the summit, and the pope himself has tried to lower expectations.

But organizers say the meeting marks a turning point in the way the Catholic Church has dealt with the problem, with Francis' own acknowledgment of his mistakes in handling the Chile abuse case a key point of departure.

"Our lack of response to the suffering of victims, yes even to the point of rejecting them and covering up the scandal to protect perpetrators and the institution has injured our people," Tagle said in his speech. The result, he said, had left a "deep wound in our relationship with those we are sent to serve."

Before the summit opened, activists in Poland pulled down a statue of a priest early Thursday after increasing allegations that he sexually abused minors. They said the stunt was to protest the failure of the Polish Catholic Church in resolving the problem of clergy sex abuse.

Video footage showed three men attaching a rope around the statue of the late Monsignor Henryk Jankowski in the northern city of Gdansk and pulling it to the ground in the dark. They then placed children's underwear in one of the statue's hands and a white lace church vestment worn by altar boys on the statue's body.

The private broadcaster TVN24 reported the three men were arrested.

Jankowski, who died in 2010, rose to prominence in the 1980s through his support for the pro-democracy Solidarity movement against Poland's communist regime. World leaders including President George H.W. Bush and British Prime Minister Margaret Thatcher visited his church in recognition of his anti-communist activity.