The UN's damning report on the Vatican's handling of child sex abuse cases has turned up the pressure on the Church to convince a sceptical international community it has adopted a zero-tolerance approach.

"The Vatican has taken some steps forward, but they have been largely symbolic: energetic words rather than actions. The UN is right to have spoken out so strongly," Vatican commentator Paolo Flores D'Arcais told AFP.

The Church was denounced by the UN Committee on the Rights of the Child on Wednesday for failing to stamp out predatory priests, and urged to hand over known and suspected abusers for prosecution.

The UN committee's recommendations are non-binding but have held up a fresh mirror to highly damaging Vatican failures.

The report was a bolt from the blue for an institution revelling in the popularity of its new pope, Francis, who has spoken little of the abuse and who appeared to hope the Church had left the crisis behind it.

Some Vatican watchers believe much has been done to set an important moral example for wayward clergy.

The accusations "belong to the past. Benedict XVI brought about a great change through his closeness to victims... praying and crying with them," said religious watcher Andrea Tornielli, who writes for newspaper La Stampa's Vatican Insider website.

But the Vatican's lack of transparency -- insisting on dealing with the scandal behind closed doors -- has disappointed victims.

For more than a decade, the Church has been rocked by a cascade of scandals around the world, with victims describing the trauma of abuse at the hands of people charged with their care.

The Vatican says it continues to receive around 600 claims against abusive priests every year, many dating back to the 1960s, 1970s and 1980s.

Former pope Benedict apologised in 2010 for the "sinful and criminal" acts committed by members of the clergy, saying he was "truly sorry" and going on to defrock 400 offenders between 2011 and 2012.

His successor Pope Francis has said Catholics should feel "shame" for abuse and has presided over the creation of a commission to investigate sex crimes, enforce prevention and care for victims -- though it has yet to begin work.

While several bishops have stepped down over scandals in their dioceses, victims and support groups demand someone be held legally accountable.

'Publicly remove offenders from ministry'

The Survivors Network of those Abused by Priests (SNAP) dismissed as inadequate the Vatican's tense response that it had "taken note" of the UN report and would submit it to "a thorough study and examination".

"Bishops don't move predators, shun victims, rebuff prosecutors, shred evidence, intimidate witnesses, discredit whistleblowers, dodge responsibility, fabricate alibis... because of inadequate 'study'," SNAP said.

"The quickest way to prevent child sexual violence by Catholic clerics is for Pope Francis to publicly remove all offenders from ministry.... But like his predecessors, he has refused to take even tiny steps in this direction," it said.

The Vatican's secretary of state Pietro Parolin spoke of the Church's "desire to adhere to the commission's needs".

But frustration over the Vatican's handling of the matter was expressed even by some Catholic groups.

"If the pope is serious about turning the page on this scandal, he should immediately dismiss any bishop who oversaw a diocese in which a priest who abused children was shielded from the civil authorities," said Jon O'Brien, head of the US lobby group Catholics for Choice.

"There can be no place in our Church for bishops or priests who put children at risk. From now on, there must be zero tolerance for bishops who shield child abusers," he said.

Whether the Vatican will take steps to enforce legal consequences for predator priests or not, it has criticised the UN's parallel request for changes to Church attitudes to abortion as going against its attempts to protect child welfare.

"The Committee on the Rights of the Child... recommends the Holy See change its position on abortion. (But) when a child is dead, it has no rights!" said Silvano Tomasi, the Vatican's permanent observer to the UN.