The Pope’s acknowledgement came only after he was asked to comment on the situation during a press conference on the flight on Tuesday.
“It’s true, there are priests and bishops who have done that,” he admitted, adding: “Should we do something more? Yes. Is there will? Yes, but it’s a path that we have already begun."
Francis went on to say that his predecessor, Pope Benedict XVI, had taken action against what he called the "sexual slavery" of nuns practiced by a priest who had founded a France-based order.
The Vatican later clarified that description on Wednesday, saying that the reference to sexual slavery was meant to illustrate the “manipulation or a type of abuse of power that is reflected in a sexual abuse”.
With the advent of the #MeToo movement, the plight of nuns, who have tried for years to call attention to their situation, has finally been heard.
In November, the International Union of Superiors General, the organisation that represents Catholic women’s religious orders, publicly denounced the “culture of silence and secrecy”. It urged nuns to report abuse to law enforcement.
Catholic nuns around the world have increasingly been reporting sexual abuse at the hands of clerics.
Last week a Vatican magazine reported on nuns aborting the children of priests and an investigation by the Associated Press last year revealed cases of abuse of nuns in Europe, Asia, Africa and South America - cases in which the Vatican had not sufficiently punished offenders or supported victims.
Mary Dispenza, a former nun who works with the American victims advocacy group, the Survivors Network of Those Abused by Priests (Snap), pushed the #Nunstoo hashtag on Twitter.
Initially she had started collecting stories about those abused by nuns, but it soon turned to stories from nuns about abuse by priests.
But that growing attention has yet to improve the lives of the victims. Last year, a Kerala nun alleged that Bishop Franco Mulakkal had raped her 13 times between 2014 and 2016. Five nuns have since pledged their support to the Kerala nun, and four were later ordered to leave the Kuravilangad convent by the head of the Jalandhar-based Missionaries of Jesus.
Abuse of power
An article written by Lucetta Scaraffia in February’s edition of Women Church World, a women’s magazine of the Vatican newspaper L’Osservatore Romono, entitled "Without any touching", argues that such abuse has remained hidden within the Catholic Church, due to the "amgibuious" role of women.
Men occupy the higher levels in the Catholic Church, it says, and they have been the one creating an atmosphere of fear for speaking up against authority.