Pope Francis has said the world expects “concrete measures” to tackle child sexual abuse by priests and not only “simple and obvious condemnations”.
At a summit to discuss the scandals that have rocked the Roman Catholic Church, he said “the cry of the little ones seeking justice” had to be heard.
Details of sexual abuse have emerged across the world and the Church has been accused of covering up crimes.
Survivors say new safeguarding protocols are needed to protect minors.
The unprecedented four-day summit at the Vatican is being attended by the heads of all national bishops’ conferences from more than 130 countries.
The Vatican has tried to reduce expectations with the Pope previously saying the conference – called Protection of Minors in the Church – represented only the beginning of a conversation.
The 82-year-old pontiff is under serious pressure to provide leadership and generate workable solutions to what is the most pressing crisis facing the modern Church.
“The holy people of God look at us and await from us not simple and obvious condemnations, but concrete and effective measures to put into place. Concreteness is required,” he said in a short opening statement.
“I ask the Holy Spirit to support us in these days and to help us to transform this evil into an opportunity for awareness and purification. May the Virgin Mary enlighten us to try to cure the serious wounds that the scandal of paedophilia has caused both in children and in believers.”
The Pope’s biggest challenge
By Martin Bashir, BBC religion editor
Pope Francis must confront the assumptions, attitudes and practices that have allowed a culture of abuse to flourish. The extent of this challenge may prove overwhelming.
This is only the beginning of an attempt to address a sickness that has been poisoning the Church since at least the 1980s, leaving its moral authority in tatters.
The focus is now firmly fixed on Pope Francis, who leads an organisation with more than 1.2 billion adherents, present in virtually every country on Earth.
His pontificate began with widespread enthusiasm for a man who chose pastoral appeal over pomp and ceremony, humility and compassion over the trappings of status. But how it ends is likely to depend on the action he takes, and the protocols he implements, to deal with the scourge of abuse.
Pope Francis called for “decisive action” on the issue when he was elected in 2013, but critics say he has not done enough to hold to account bishops who allegedly covered up abuse.
Thousands of people are thought to have been abused by priests.
Observers argue that implementing universal protocols is challenging because the Church exists in a range of cultures and judicial systems.
Although progress has been made in some countries, in other places it is still not considered to be a priority. Some churches in Asia and Africa, in particular, even deny the problem exists.
Archbishop of Manila Cardinal Luis Antonio Tagle told the summit clerical abuse took place because of a misuse of power.
But many, including conservative critics of Pope Francis, challenge this view and believe homosexuality is the real root cause of the abuse.
As the event started, one of its four organisers – Archbishop of Mumbai Oswald Gracias, one of the Church’s most senior cardinals – admitted that he could have better handled allegations that were brought to him.
Some groups of survivors have voiced scepticism that any concrete action will be taken during the event, calling it a publicity stunt aimed at cleansing the image of the Church.