In Pictures: Pope Francis winds up Portugal visit with big outdoor mass

Pope Francis celebrated an open-air Mass before a huge crowd on Sunday at a riverside park near Lisbon to wrap up an international jamboree of Catholic youth.

Around 1.5 million people attended the service at the Parque Tejo park on the outskirts of the Portuguese capital, the Vatican said.

Pope Francis arrives to lead the holy mass for World Youth Day at Parque Tejo during his apostolic journey to Portugal on the occasion of the XXXVII World Youth Day, in Lisbon, Portugal.

Portugal's President Marcelo Rebelo de Sousa (2-L), accompanied by the Prime Minister Antonio Costa (2-R) and Lisbon Mayor Carlos Moedas (L), attends the Holy Mass led by Pope Francis on the last day of World Youth Day (WYD) at Parque Tejo in Lisbon, Portugal.

The crowd waved national flags and cheered as the 86-year-old pope arrived at the park, which was built for the occasion on a former landfill site. Many had camped out overnight in sleeping bags or floor mats.

With little shade in the park, pilgrims protected themselves from the sun with umbrellas or makeshift tents made from sheets.

The weather is a concern with temperatures expected to soar to 41 degrees Celsius (106 degrees Fahrenheit).

People gather as Pope Francis leads the holy mass for World Youth Day at Parque Tejo, during his apostolic journey to Portugal on the occasion of the XXXVII World Youth Day, in Lisbon, Portugal.

World Youth Day, created in 1986 by John Paul II, is the largest Catholic gathering in the world and features a wide range of events, including concerts and prayer sessions.

Pope Francis announced that the next edition would be held in Asia for the first time in three decades. News that Seoul, South Korea would host World Youth Day in 2027 was a reflection of the continent's increasing importance to the Catholic Church.

Pilgrims attend the closing mass of the World Young Day (WYD), officiated by the pope in Tejo Park, Lisbon.

The Argentine pope is in increasingly fragile health, and now uses a wheelchair or walking stick to get around. This is his first foreign trip since he spent nine nights in hospital after undergoing hernia surgery in June.