Senior UN rights experts revealed Monday they had written to the Vatican urging them to end child sex abuse in Catholic institutions, to punish the guilty and compensate the victims.

The four special rapporteurs, who do not speak for the United Nations but report their findings to it, wrote to the Vatican in April, but only released their letter on Monday.

In it, they voiced their "utmost concern about the numerous allegations around the world of sexual abuse and violence committed by members of the Catholic Church against children".

They expressed concern about what they said were Church measures to "protect alleged abusers, cover up crimes, obstruct accountability of alleged abusers, and evade reparations due to victims".

And they called for "all necessary measures" to be taken to stop any further abuse of children in Catholic institutions.

The Church should also ensure that "those responsible are held to account and reparations are paid to victims", they added.

Referring to persistent allegations of Church officials' obstruction of legal proceedings seeking accountability and reparations, the experts urged the Vatican to cooperate fully with law enforcement in the countries concerned.

They should hold off signing agreements that would allow accused church members to escape accountability, they said.

The letter was penned by the special rapporteurs on the sexual exploitation of children; on torture, cruel and degrading treatment; on the promotion of truth, justice and reparation; and on the rights of persons with disabilities.

Pervasiveness' of abuse 

All four signatories expressed concerned about what it said were continued attempts to undermine legislative efforts to prosecute child sex offenders.

The request by Pope Francis that officials report crimes to civil authorities was not yet mandatory, they pointed out.

All offences needed to be prosecuted to send "a clear signal to all members of the Catholic Church that such violations will never again be tolerated", the rapporteurs said.

They noted with concern "the apparent pervasiveness of child sexual abuse cases and the apparent systematic practice of covering up and obstructing the accountability of alleged abusers belonging to the Catholic Church".

Their letter also noted the lack of response to a previous letter one of the rapporteurs has sent in 2019 on alleged abuse in several countries.

Their letter came before the discovery in May of the remains of 215 children at the site of a religious residential school for indigenous children in Canada.

Pope Francis has so far not offered the apology that many people, including the Canadian government, have been calling for.