VATICAN CITY (UPDATE)- Pope Francis on Thursday opened a landmark Vatican summit on fighting child sex abuse, saying the world expected "concrete measures" on tackling pedophilia in the Catholic Church.

Over the next 3 and-a half days, the pontiff will hold talks with bishops from around the world to discuss the Church's response to child abuse by members of the clergy.

"The holy people of God looks to us, and expects from us not simple and predictable condemnations, but concrete and effective measures to be undertaken. We need to be concrete," he said as the summit opened, the first of its kind.

"Hear the cry of the little ones who plead for justice."

The ongoing scandal has again escalated in a crisis which has touched many countries across the globe, with recent cases affecting Chile, Germany and the US.

The 82-year-old pontiff hopes to raise awareness about abuse through prayers, speeches, working groups and testimonies from victims.

He said the summit was a moment to "turn this evil into an opportunity for awareness and purification" and "heal the grave wounds that the scandal of pedophilia has caused, both in the little ones and in believers."

'MURDERERS OF THE SOUL'

Those gathered heard from unnamed abuse survivors, one of whom told them: "You are the physicians of the soul and yet, with rare exceptions, you have been transformed -- in some cases -- into murderers of the soul, into murderers of the faith."

Another, a woman, described the horrors of being forced to undergo three abortions after being abused by a priest.

The summit aims to educate 114 top bishops who will then return home with clear ideas on how to spot and deal with abuse and pedophilia.

"We humbly and sorrowfully admit that wounds have been inflicted by us bishops on the victims and in fact the entire body of Christ," Manila Archbishop Luis Antonio Cardinal Tagle told the assembly.

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

The scale of the task has been further complicated by the fact that some churches, in Asia and Africa in particular, deny the problem exists.

Cardinal Blase Cupich, one of the pope's trusted allies in the United States and one of the summit's four organizers, said he hoped people "see this as a turning point."

The US Catholic Church is undergoing one of the worst crises in its history following last week's defrocking of a former cardinal -- American Theodore McCarrick -- for sexually abusing a teenager 50 years ago.

Three themes -- responsibility, accountability and transparency -- form the backbone of the summit and will provide its participants with the keys to ensuring child safety, he said.

'VULNERABLE'

There are reforms in the pipeline, such as the "tweaking" of some parts of canon law, said Maltese Archbishop Charles Scicluna, another of the organizers.

But the suggestion that Church laws only need fine-tuning has angered many, including Anne Barrett Doyle, the co-director of BishopAccountability.org, a public database that documents cases of proven or suspected sex crimes by clerics.

"Canon law has to be changed, not tweaked, not modified, but fundamentally changed, so that it stops prioritizing the priesthood... over the lives of children, and vulnerable adults who are sexually assaulted by them," she said.

Scicluna insisted that summoning Church leaders from across the globe to Rome "is, in itself, a very important message."

He spent 10 years as the Vatican's top prosecutor of pedophilia cases and was picked by Francis to travel to Chile last year to hear from victims whose voices had previously been silenced by an internal Church cover-up.

Scicluna has called for an end to the code of silence and culture of denial within the beleaguered centuries-old institution.

"We have to face facts because only the truth of the matter, and confronting the facts, will make us free," he added.