Pope Francis to meet victims of sex abuse by Catholic priests at Vatican

Pope Francis has said he will meet a group of sex abuse victims at the Vatican early next month, and will show zero tolerance for anyone in the Catholic Church, including bishops, who abused children.

"Sexual abuse is such an ugly crime ... because a priest who does this betrays the body of the Lord. It is like a satanic Mass," he said on the way back from his Middle East visit.

It was some of the toughest language he has used on a crisis that has rocked the church for more than a decade.

"We must go ahead with zero tolerance," he said, adding that three bishops were under investigation.

Francis said he would meet eight victims and Cardinal Sean Patrick O'Malley of Boston, who is head of a commission studying ways of dealing with the crisis.

Speaking to reporters for more than an hour on the plane taking him back from a visit to the Middle East, the pope looked alert despite the gruelling three-day trip.He overruled his spokesman who suggested the airborne news conference be cut short to allow him to rest.

The 77-year-old pontiff fielded questions on a range of topics, including Vatican finances, his concern for the environment, and whether he himself would one day retire like his predecessor Benedict XVI.

The concept of a "pope emeritus" could someday become normal in the church, he said.

During his trip he invited Israeli President Shimon Peres and Palestinian President Mahmoud Abbas to the Vatican next month.

The pope said the meeting would not be a mediation but a prayer meeting that he hoped could encourage the stalled peace process.

Francis said that next month, sex abuse victims would attend his morning mass and then he would meet them.

It will be the first time Francis has met sexual abuse victims since his election in March last year.

But it was not clear if the pope also meant zero tolerance for bishops who are not accused of being abusers themselves but who are accused of having turned a blind eye to abuse by priests in their dioceses or who may have covered up abuse scandals.

O'Malley said last month in Rome that the commission he heads will recommend that negligent clerics be held accountable regardless of their rank in the church.

In many cases of abuse, most of which took place decades ago but surfaced in the past 15 years or so, bishops seeking to protect the church's reputation moved priests from parish to parish instead of defrocking them or handing them over to police.

Victims' groups have pressed the Vatican to hold bishops who either shielded abusers or were negligent in protecting children to account, along with abusers themselves.

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 Vatican called the report unfair and ideologically slanted.