Vatican officials are expected to face tough questions from the UN on the sexual abuse of thousands of children by Catholic clergy, BBC News reports.

Members of the Holy See - the city state's diplomatic entity - will be grilled by a UN committee in Geneva.

The Vatican refused an earlier request for information, saying the cases were the responsibility of the judiciary of countries where abuse took place.

The Pope has said dealing with abuse is vital for the Church's credibility.

The Catholic Church has faced a raft of allegations of child sex abuse by priests around the world and criticism over inadequate responses by bishops.

Last month, Pope Francis announced that a Vatican committee would be set up to fight sexual abuse of children in the Church and offer help to victims. He has also strengthened Vatican laws on child abuse, broadening the definition of crimes against minors to include sexual abuse of children.

The Holy See is a signatory to the UN Convention on the Rights of the Child, a legally-binding instrument which commits it to protecting and nurturing the most vulnerable in society. The Holy See ratified the convention in 1990.

Its first and only progress report was submitted in 2012 after intense criticism following 2010 revelations of child sex abuse cases in Europe and beyond.

The Committee on the Rights of the Child (UNCRC) is expected to ask wide-ranging questions, forcing the Holy See to defend itself in public for the first time. It faces allegations that it enabled the sexual abuse of thousands of children by protecting paedophile priests at the expense of victims.

Last July, the UN Committee requested detailed information about the particulars of all sexual abuse cases notified to the Vatican since 1995.

The questions included whether priests, nuns and monks guilty of sexual crime were allowed to remain in contact with children, what legal action had been taken against them, and whether complainants were silenced.

In its response, the Holy See insisted that it was "separate and distinct" from the Roman Catholic Church, and that it was not its practice to disclose information about the religious discipline of clergy unless requested by the authorities in the country where they were serving.

It stressed that it had changed the criteria for choosing priests and revised Church law to ensure clergy were properly disciplined.