Pope Francis in US
Pope Francis celebrates his final mass of his visit to the United States at the Festival of Families on Benjamin Franklin Parkway in Philadelphia, PennsylvaniaJim Bourg/Reuters

Pope Francis has said he was "overwhelmed by shame" at the sexual abuse of children by the clergy. Wrapping up his 10-day visit to Cuba and the US, he addressed sex abuse allegations by Catholic priests as he met some of the victims.

During his 90-minute private meeting with the victims, Francis said he was "deeply sorry" for the incidents and added "God weeps" for their sufferings. Many of the victims are furious that the Vatican has not properly dealt with allegations surrounding sexual abuse incidents involving the Roman Catholic Church in the US.

"For those who were abused by a member of the clergy, I am deeply sorry for the times when you or your family spoke out, to report the abuse, but you were not heard or believed. Please know that the Holy Father hears you and believes you. I deeply regret that some bishops failed in their responsibility to protect children," the 78-year old said in his message to the victims.

Subsequent to his informal meeting with the victims, the pope brought Philadelphia to a standstill with his final mass, an emotional farewell to the US. Nearly one million faithful participated in the mass under an autumnal sky in the Benjamin Franklin Parkway.

Speaking in Spanish at the open-air mass on the steps of the Philadelphia Museum of Art, Francis, often hailed as the people's pope, said: "The urgent challenge of protecting our home includes the concern of bringing all of the human family together in the pursuit of sustainable and integral development."

The mass was a culmination of an event called World Meeting of Families. Church officials said the next such event would take place in Dublin in 2018.

More about Pope Francis in US