Pope Francis on Sunday declined to comment on a letter by a former Vatican official that he had ignored sexual abuse claims against US cardinal Theodore McCarrick, who was forced to resign last month.
"I will not say a word about that. I think that the communique speaks for itself," the pontiff said when questioned by journalists on his plane, flying back to Rome after his visit to Ireland.
While in Ireland earlier in the day, Pope Francis "begged for God's forgiveness" for multiple abuse scandals within the Irish church but faced accusations by a former Vatican official that he had personally ignored allegations against senior clergy.
Pope Francis aboard the flight to Rome at the end of his two-day visit to Ireland. Source: AAP
In front of 45,000 supporters at the rain-soaked Knock shrine in the west of Ireland, the pope spoke of the "open wound" of the Church's sexual abuse scandal and demanded "firm and decisive" measures to find "truth and justice".
He said Mass to tens of thousands of flag-waving worshippers at Dublin's Phoenix Park, before heading back to Rome after his two-day visit to the former Catholic stronghold.
He also acknowledged other abuses by the Irish church, including at its so-called "mother and baby" homes for unwed mothers.
But in the centre of the Irish capital around 5,000 abuse victims and their supporters braved the weather to attend the "Stand for Truth" rally.
A woman dressed as a nun, with fake blood on her hands, and a man handing out homemade placards reading "the church protects pederasts" were among those protesting.
"I think it's obviously causing quite a lot of distress," abuse victim and campaigner William Gorry said of the visit.
"Healing is something that's going to take a long, long time if it's going to happen at all," he told AFP.
At another "Nope to the Pope" demonstration, protesters called for gay and transgender recognition, a clearer separation of religion and state in Ireland and the acceptance of contraception by the Vatican -- as well as action on abuse.
"I think he should get on his knees and beg forgiveness of the people of Ireland," Lisa Barcaen, who was dressed as a nun with fake blood on her hands, told AFP.
Papal 'cover up'
The scandal has dogged the pope's visit, and intensified overnight when a former Vatican envoy to the United States accused Francis of personally ignoring sexual abuse claims against prominent US cardinal Theodore McCarrick, who was forced to resign last month.
Archbishop Carlo Maria Vigano wrote in a letter published in the National Catholic Register that he had told Francis of the allegations in 2013, but that he had responded by lifting sanctions imposed on McCarrick by his predecessor pope Benedict.
"He (Pope Francis) knew from at least June 23, 2013, that McCarrick was a serial predator," wrote Vigano," adding that "he knew that he was a corrupt man, he covered for him to the bitter end."
The Vatican said it had no comment to make on the claims.
Irish Prime Minister Leo Varadkar on Saturday directly urged the pope to take action against abuses and ensure justice for victims worldwide.
"Holy Father, I ask that you use your office and influence to ensure that this is done here in Ireland and across the world," he said, calling the scandals a "stain" on the church and state.
The pope met eight abuse victims on Saturday, including a woman assaulted by a priest when she was in hospital aged 13.
Paul Jude Redmond, who was illegally adopted from a Church-run "mother and baby home" because his mother was unmarried, also met the pope. He said the pontiff appeared "genuinely shocked" by the stories of abuse.
But at a news conference in Dublin on Saturday by the group Ending Clergy Abuse (ECA), victim Mark Vincent Healey said the pope's speech in Dublin was a "total missed opportunity".
"We're still waiting. We're left with uncertain silence. When is he going to act? What is he going to do?"
Students from St Patrick's National School, Cloonlyon wait the arrival of Pope Francis. Source: AAP
Silent vigil
The pontiff went to Ireland to close the 2018 World Meeting of Families (WMOF) -- a global Catholic gathering that addressed issues including the treatment of gay people in the Church.
It was the first papal visit to Ireland since John Paul II spoke in front of 1.5 million people during a visit in 1979.
The Church's role and standing has been badly dented by the abuse scandals and the Irish have shed traditional Catholic mores, voting earlier this year to legalise abortion after approving same-sex marriage in 2015.
In Tuam, a town in western Ireland not far from Knock, hundreds joined in a silent vigil on Sunday in solidarity with victims of the "mother and baby" homes -- institutions accused of being punishment hostels for unwed pregnant women.
"Significant quantities" of baby remains found in makeshift graves at the site of one such home in Tuam last year shocked the country.
Pope Francis during his visit to the Capuchin Day Centre for the Homeless in Dublin. Source: AAP
Multiple probes in Ireland have found Church leaders protected hundreds of predatory priests and former Irish president Mary McAleese revealed this month that the Vatican had sought to keep Church documents inaccessible to government investigators.
The abuse scandals in Ireland are part of a worldwide crisis for the Vatican.
A devastating report earlier this month accused more than 300 priests in the US state of Pennsylvania of abusing more than 1,000 children since the 1950s.
