Pope Francis, whose papacy has been marked by efforts to quell a global crisis over sexual abuse of children by Catholic clergy, said on Tuesday he was committed to stopping the abuse of nuns by priests and bishops, some of whom had used the women as sex slaves.

Francis made his comments on the plane returning from Abu Dhabi in response to a reporter's question about an article last week in a Vatican monthly magazine about the abuse of nuns in the Catholic Church.

Recently more nuns, encouraged by the #MeToo movement, have been coming forward to describe abuse at the hands of priests and bishops. Last year, the International Union of Superiors General, which represents more than 500,000 Catholic nuns, urged their members to report abuse.

'It is true...there have been priests and even bishops who have done this. I think it is still going on because something does not stop just because you have become aware of it,' Francis said.

'We have been working on this for a long time. We have suspended some priests because of this,' he said, adding that the Vatican was in the process of shutting down a female religious order because of sexual abuse and corruption. He did not name it.

'I can't say "this does not happen in my house." It is true. Do we have to do more? Yes. Are we willing? Yes,' he said.

Francis said former Pope Benedict dissolved a religious order of women shortly after his election as pontiff in 2005 'because slavery had become part of it (the religious order), even sexual slavery on the part of priests and the founder'.

He did not name the group but Vatican spokesman Alessandro Gisotti said it was a French order.

Before he became pope, Benedict was Cardinal Joseph Ratzinger, the head of the Congregation of the Doctrine of the Faith, the Vatican department that investigates sexual abuse. The pope at the time was John Paul.

Then-cardinal Ratzinger wanted to investigate the religious order where women were being abused but he was blocked, Francis said, without saying who prevented the probe.

After he became pope, Ratzinger reopened the investigation and dissolved the order, Francis said.

Pope Francis has summoned key bishops from around the world to a summit later this month at the Vatican to find a unified response on how to protect children from sexual abuse by clergy.

Asked if there would be some kind of similar action to confront abuse of nuns in the Church, he said: 'I want to move forward. We are working on it.'