Pope Francis took time out from the crowds in Philadelphia on Sunday to visit a prison, telling inmates that all people need to be "cleansed" and they should not view their confinement as exclusion from society.

Meeting 60 men and 11 women prisoners in a drab room at the Curran-Fromhold Correctional Facility, the Argentine-born pope stressed their time behind bars was meant to rehabilitate them. He then shook hands with each inmate, blessing all and hugging some who rose to greet him.

Francis has emphasized outreach to the poor, to immigrants and those on the margins of society throughout his first visit to the United States. He lunched with homeless people in Washington on Thursday after addressing the U.S. Congress.

"All of us need to be cleansed, to be washed, all of us, and me in the first place," the Argentina-born pope said in his native Spanish at the prison, which houses some 2,800 inmates.

"This time in your life can only have one purpose: to give you a hand in getting back on the right road," he told the inmates and assembled family members. "All of us are part of that effort."

When he entered the hall, prison officials led Francis to an upholstered wooden chair that inmates had made for his visit. He pointed to the seat, gave the waiting inmates a thumbs-up sign and then blew them a kiss after he sat in it.

"The chair is very beautiful," he told them. "Thank you very much for the hard work."

Mildred Nawa, 51, a nurse from Reading, Pennsylvania, said she was glad the pope was meeting with prisoners.

"I think that is what he should be doing, reaching out to the people who really need him. I think he is more about living by like Jesus than focussing on dogma," she said in downtown Philadelphia while waiting for a papal Mass later on Sunday. "I think it's a great example for priests, for all of us."

Francis, who has called for the global abolition of the death penalty and also has spoken against lengthy prison terms, has made prison visits a regular part of his travels. He has counselled teenagers in juvenile detention in Brazil and in Bolivia, he kissed inmates in the country's most violent prison.

Maria Lazar, a 70-year-old Catholic from Harleysville, Pennsylvania, also on her way to the Mass, said the visit underlined the pope's message of tolerance.

"It's about forgiveness, it reminds people that no matter what you have done on your life you can always turn back," Lazar said. "And it helps remind us not to judge, that we all have our issue.