Pope Francis has asked for forgiveness for child sex abuse carried out by priests.

The pontiff's apology, which was reported by Vatican Radio, is his strongest statement on the issue since he was elected last year.

"I feel compelled to personally take on all the evil which some priests, quite a few in number, [but] obviously not compared to the number of all the priests, to personally ask for forgiveness for the damage they have done for having sexually abused children," he said at a meeting with members of a children's charity.

"The (Catholic) Church is aware of this damage, it is personal, moral damage carried out by men of the Church, and we will not take one step backward with regards to how we will deal with this problem and the sanctions that must be imposed.

"On the contrary, we have to be even stronger. Because you cannot interfere with children."

Francis was meeting with members of International Catholic Child Bureau, which works to protect the rights and dignity of children worldwide.

He did not specify whether "sanctions" would be church-enforced or involve civil justice authorities.

In February the United Nations Committee on the Rights of the Child accused the Vatican of systematically turning a blind eye to decades of abuse and attempting to cover up sex crimes.

The scathing report urged the church to immediately hand over its records on the abuse of tens of thousands of children, immediately remove anyone suspected of abuse from their post and refer the matter to civil legal authorities.

The Vatican called the report unfair and ideologically slanted.

The Pope's words strike a different tone to comments he made in March to an Italian newspaper in which he defended the church's record.

"The Catholic Church is perhaps the only public institution that has moved with transparency and responsibility. No-one has done more, and yet the church is the only one that is being attacked," he was quoted as saying by Corriere della Sera in comments decried by victims' rights groups.

Thousands of cases of abuse by priests have come to light over the past decade and the Catholic Church is regularly accused of trying to cover up the crimes.

But the Vatican has vowed a zero-tolerance approach and has begun implementing prevention and detection measures to root out abuse, although this varies widely between different countries.

Francis's predecessor Benedict XVI had also made a personal apology for the abuses.

AFP/Reuters