ABOARD THE PAPAL PLANE — Pope Francis said on Tuesday that the Roman Catholic Church had faced a persistent problem of sexual abuse of nuns by priests and even bishops, the first time he has publicly acknowledged the issue.

Catholic nuns have accused clerics of sexual abuse in recent years in India, Africa, Latin America and in Italy, and a Vatican magazine last week mentioned nuns having abortions or giving birth to the children of priests. But Francis has never raised the issue until he was asked to comment during a news conference aboard the papal plane returning to Rome from his trip to the United Arab Emirates.

“It’s true,” Francis said. “There are priests and bishops who have done that.”

The pope’s admission opens a new front in the long-running scandal of sexual abuse by priests, recognizing nuns who have tried for years to call attention to their plight. With the #MeToo movement going strong, and Francis under pressure for neglecting the victims of child abuse, the nuns’ pleas have gained traction.

In November, the organization representing the world’s Catholic women’s religious orders, the International Union of Superiors General, publicly denounced the “culture of silence and secrecy” that contributed to abuse, and urged nuns to report abuse to law enforcement.