LISBON - Pope Francis visited a Church-run social centre in a low-income Lisbon neighbourhood Friday, urging young people to shun "distilled," orderly lives where everything seems perfect but to "get your hands dirty" by helping the needy.

During his address at the St. Vincent de Paul parochial centre in the Serafina neighbourhood, Francis said he was having trouble with his glasses and found it hard to read, so he put aside his prepared speech and went off script.

"Tangible love is that which gets its hands dirty," he said.

The 86-year-old pope is in Lisbon for the Catholic Church's World Day of Youth festival, which ends on Sunday. On Wednesday evening one about half a million people - one of the biggest crowds ever seen in Portugal - attended an opening rally.

"How many distilled, useless, lives pass through life without leaving a mark because their lives don't have weight," he said in an address to workers and volunteers at the social centre after a children's choir sang for him.

He said the message he wanted to leave young people attending the festival from around the world was that while abstract, platonic love exists "in orbit", tangible love can change the world.

Francis spoke of the superficiality of people who help the poor to make themselves feel good but who then immediately wash their hands in disgust.

"Through your actions, your commitment, by getting your hands dirty, by touching the reality and misery of others, you are creating inspiration, you are generating life," he said.

On Friday morning, Francis heard the confessions of three young Catholics, from Spain, Italy and Guatemala, in one of the parks hosting the festival.

The event comes less than six months after a report by a Portuguese commission said at least 4,815 minors were sexually abused by clergy - mostly priests - over seven decades.

Amelia Grantham, a 28-year-old from Birmingham, England, who was one of the people lined up to have her confession heard by a priest, said it was important for the Church to admit its scandals.

"The misdeeds of some are the shame of all and we have to own that," Grantham said. "But also that there's hope."

(Reporting by Philip Pullella, Editing by Louise Heavens)