Pope Francis spoke to youths in Paraguay, encouraging them to "make a mess." Pictured: Pope Francis waves as he leads his Sunday Angelus prayer in St. Peter's Square at the Vatican, June 28, 2015. Reuters/Alessandro Bianchi

ASUNCION (Reuters) - Pope Francis, drawing to a close his three-country tour of South America, on Sunday urged tens of thousands of youths in Paraguay to look after their less fortunate peers and fight for a dignified life filled with hope and strength.

"They wrote a speech for me to give you. But speeches are boring," the Argentine pontiff said to loud cheers. "Make a mess, but then also help to tidy it up. A mess which gives us a free heart, a mess which gives us solidarity, a mess which gives us hope."

It was not the first time Francis has called on young people to shake things up, repeating a mantra he voiced in Brazil in 2013 when he urged youngsters to demand a more outward-looking Catholic church.

"We don't want young weaklings. We do not want young people who tire quickly, who live life worn out with faces of boredom. We want youths with hope and strength," Francis told the rally, as night fell over the banks of the Paraguay River outside the capital.

Earlier on Sunday, the pope heard harrowing tales of life in a flood-prone shantytown and appealed to the slum dwellers, many of whom had been forced from their farms and now squat on city land, to stay united in their struggle for better living and working conditions.

The Argentine pontiff has made defending the poor a major theme of his "homecoming" trip, which also took him to Ecuador and Bolivia, ranked among Latin America's poorest countries. On Saturday night, he appealed to world leaders and business executives to seek a new economic model to help the destitute.

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Pope Francis greets the crowd of faithful from a popemobile in Quito, Ecuador, July 5, 2015. Francis landed in Ecuador's capital Quito on Sunday to begin an eight-day tour of South America that will also include visits to Bolivia and Paraguay. On his first visit as pontiff to Spanish-speaking Latin America, the Argentina-born pope is scheduled to conduct masses in both Quito and the coastal city of Guayaquil before flying to Bolivia on Wednesday. Reuters/Kevin Granja

In the Banado Norte neighborhood of Asuncion, Paraguay, murals adorned the walls of houses made of corrugated metal, wood and cement blocks. One of them read: "Yes to life, no to drugs, fight for change."

"We built our neighborhoods inch by inch, overcoming difficult terrain, floods and hostile public authorities," Maria Garcia, a local organizer, told him. "It's been a tough fight to put up a home in the midst of hardship, but we never gave in nor let ourselves be swept away by sadness."

Idolatry of Money

From Banado Norte, the pope went to hold a mass for more than a million people in an unused air base.

The altar's backdrop was designed by a local artist who used corn cobs, coconuts, squashes, beans, seeds and other local produce to create huge murals of St. Francis of Assisi, from whom the pope took his name, and St. Ignatius of Loyola, the founder of the Jesuits, the religious order to which he belongs.

Argentine President Cristina Fernandez flew in to attend the mass and greeted Francis at the altar at the end of the service. She and Francis had a tricky relationship when he was an archbishop, because of his criticisms of corruption and their differing views on social issues like gay marriage.

On his trip, Francis has used two major speeches to excoriate unbridled capitalism and champion the rights of the poor. He has also warned of irreparable damage to the planet.

In Bolivia on Thursday, he urged the downtrodden to change the world economic order and called for the poor to have the "sacred rights" of labor, lodging and land.

On Saturday, he urged politicians and business leaders "not to yield to an economic model which is idolatrous, which needs to sacrifice human lives on the altar of money and profit". Food and shelter were essential to human dignity, he said.

He said those charged with promoting economic development must ensure it had "a human face," and he blasted "the idolatry of money and the dictatorship of an impersonal economy lacking a truly human purpose."