A nun and a woman journalist have delivered the toughest criticism of church leaders heard so far at Pope Francis' sexual abuse conference, accusing them of hypocrisy and covering up horrendous crimes against children.

About 200 senior church officials, all but 10 of them men, listened at times in stunned silence in a Vatican audience hall as the women read their frank and at times angry speeches on Saturday, the penultimate day of the conference convened by the Pope to confront a worldwide scandal.

Sister Veronica Openibo, a Nigerian who has worked in Africa, Europe and the United States, spoke with a soft voice but delivered a strong message, telling the prelates sitting before her: "This storm will not pass.

"We proclaim the Ten Commandments and parade ourselves as being the custodians of moral standards and values and good behaviour in society. Hypocrites at times? Yes! Why did we keep silent for so long?" she said.

She told the pope, sitting near her on the dais, that she admired him because he was "humble enough to change your mind", apologise and take action after he initially defended a Chilean bishop accused of covering up abuse. The bishop later resigned.

"How could the clerical church have kept silent, covering these atrocities? The silence, the carrying of the secrets in the hearts of the perpetrators, the length of the abuses and the constant transfers of perpetrators are unimaginable," she said.

"We must acknowledge that our mediocrity, hypocrisy and complacency have brought us to this disgraceful and scandalous place we find ourselves as a church. We pause to pray, Lord have mercy on us!" Openibo said.

Valentina Alazraki, 64, a Mexican television reporter who, having covered five papacies, is the doyen of the Vatican press corps, told the bishops she was speaking as a woman and mother as well as a journalist.

"For a mother, there are no first or second-class children: there are stronger children and more vulnerable ones. Nor are there first and second-class children for the church," she said.

"(The Church's) seemingly more important children, as are you, bishops and cardinals - I dare not say the Pope - are no more so than any other boy, girl or young person who has experienced the tragedy of being the victim of abuse by a priest," she said forcefully in Spanish.

Alazraki told the bishops they could no longer "play ostrich" and bury their heads in the sand.

Alazraki, who was applauded at the end of her speech, also spoke of cases of corruption where religious orders and church officials hid abuse because "money, compensation, gifts" or other illegal or unethical activity.

Earlier, German Cardinal Reinhard Marx called for more "traceability and transparency" such as limiting secrecy in cases of abuse handled by the Vatican, releasing more statistics and publishing judicial procedures.

"Files that could have documented the terrible deeds and named those responsible were destroyed, or not even created. Instead of the perpetrators, the victims were regulated and silence imposed on them," Marx, a leading progressive, said.

"The rights of victims were effectively trampled underfoot, and left to the whims of individuals," he added.