Pope Francis has announced he will meet a group of sex abuse victims next month after comparing the "ugly crime" to performing "a satanic Mass".
Speaking after his Middle East tour, Pope Francis said he will show zero tolerance for anyone in the Roman Catholic Church who abuses children.
"Sexual abuse is such an ugly crime ... because a priest who does this betrays the body of the Lord," he said.
The Pope, 77, spoke to reporters for nearly an hour on his flight to Rome.
The BBC's Jeremy Bowen, who travelled with the pontiff, said many Catholics will be glad to hear Pope Francis taking a tough stance.
But it remains unclear if the Pope's zero tolerance policy will extend to bishops who are accused of turning a blind eye to abuse by priests in their dioceses.
Pope Francis said he would meet eight victims and Cardinal Sean Patrick O'Malley, who is head of a commission set up by the Vatican to investigate sex crimes committed by priests and to care for victims.
Cardinal O'Malley said last month he will recommend that negligent clerics be held accountable regardless of their rank in the Church - a move that victims' groups have pressed the Vatican on.
Jeremy Bowen, BBC News, Rome
On the plane back to Rome, Pope Francis said that the sexual abuse of children by priests was as bad as performing a satanic Mass. Scandals involving priests abusing children sexually and in other ways have caused enormous damage to Catholicism.
Secular people might say that paedophilia is actually much worse than a satanic rite. But for a pope to compare crimes carried out by Catholic priests to worshipping the devil counts as strong language.
The Pope is saying what many Catholics who have been horrified by repeated child sex abuse scandals want to hear. But he will have to follow his words with actions if he wants to stop scandals doing any more damage to the church.
For his pledge of zero tolerance to mean anything he will, eventually, have to punish the guilty men - and those higher in the Catholic hierarchy who covered up what they did.
The Pope is under pressure to act after the UN recently published a report accusing the Vatican of systematically placing the "preservation of the reputation of the Church over the protection of child victims."
Earlier on Monday, the Pope called for an end to religious intolerance during a mass in Jerusalem at the room where Christians believe Jesus held the Last Supper.
He visited the most important holy sites for Muslims and Jews in Jerusalem's Old City on the final day of his Middle East tour.
The pontiff has been feted by Israel and the Palestinians, and has invited their presidents to the Vatican.
Both Israel's Shimon Peres and Palestinian leader Mahmoud Abbas have given a positive response.
But Pope Francis sought to play down the importance of his invitation, saying he was not qualified to be a mediator and that proper negotiations were necessary for a peace deal.
"We are coming just to pray, then everyone goes home," he said. "But I think prayer is important: praying together."
Our correspondent says the Pope's visit to the region will have made him more aware of the tangled politics of peacemaking.
Catholic Church abuse scandals
- Germany - A priest, named only as Andreas L, admitted in 2012 to 280 counts of sexual abuse involving three boys over a decade
- United States - Revelations about abuses in the 1990s by two Boston priests, Paul Shanley and John Geoghan, caused public outrage
- Belgium - The bishop of Bruges resigned in April 2010 after admitting that he had sexually abused a boy for years
- Italy - The Catholic Church in Italy admitted in 2010 that about 100 cases of paedophile priests had been reported over 10 years
- Ireland - A report in 2009 found that sexual and psychological abuse was "endemic" in Catholic-run industrial schools for most of the 20th Century