PANAMA CITY -- Pope Francis is bringing World Youth Day to Panama's juvenile delinquents who can't participate in the Catholic Church's big festival of faith.

Francis on Friday will celebrate a special penitential Mass inside the Las Garzas de Pacora detention centre, which is Panama's main youth lockup. In a twist, he will also hear the inmates' confessions inside confessionals the detainees made themselves.

It's all part of Francis' belief that prisoners deserve the same dignity as everyone else -- as well as hope.

Francis opened his first full day in Panama with that message of hope Thursday, formally welcoming tens of thousands of pilgrims to World Youth Day at a twilight pep rally at the capital's seaside park.

He urged them to be builders of bridges of encounter, not "builders of walls that sow fear and look to divide and box people in," a clear reference to the proposed U.S.-Mexico border wall.

Earlier in the day, in remarks to President Juan Carlos Varela, he warned that those same young people are increasingly demanding that public officials live honest lives that are coherent with the jobs entrusted to them.

"They call upon them to live in simplicity and transparency, with a clear sense of responsibility for others and for our world," Francis told Varela and other Panamanian leaders. "To lead a life that demonstrates that public service is a synonym of honesty and justice, and opposed to all forms of corruption."

Transparency International estimates that as much as 1 per cent of Panama's GDP, approximately US$600 million, may have been lost to various corruption schemes during the presidency of Ricardo Martinelli, who governed Panama from 2009 to 2014. Martinelli was extradited to Panama last year from the United States to face political espionage and embezzlement charges.

In addition, two of Martinelli's sons have been detained in the U.S. and are being sought on corruption charges in Panama. They are suspected of receiving more than $50 million in "undue payments" from Brazilian construction giant Odebrecht, which is at the centre of one of the largest graft scandals in history.

Odebrecht has acknowledged paying nearly $800 million dollars in bribes in a dozen Latin American nations in return for favours and works contracts.

That includes at least $59 million in Panama, although authorities say the real figure is likely much higher. In addition to the Martinelli sons, the scandal has already implicated former government ministers under the elder Martinelli as well as people linked to the party of the current president, Varela.

The Martinelli family has denied involvement by the sons in the bribery scandal and alleges persecution by political foes. The former president also denies any wrongdoing and says he is being targeted politically.

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Associated Press writer Peter Orsi contributed from Mexico City