RIO DE JANEIRO (AFP) - Pope Francis celebrated Sunday mass with three million pilgrims jammed onto a Brazilian beach, wrapping up a landmark trip to reignite the Catholic faith in a festive atmosphere with young believers.

Latin America's first pontiff was given a rock star's welcome on Rio de Janeiro's legendary Copacabana beach, with a sea of faithful waving flags, dancing and chanting "long live the pope!" on the crescent-shaped shoreline.

The head of the world's 1.2 billion Roman Catholics hammered home his plea for young believers gathered for World Youth Day to "go and make disciples of all nations" as he concluded his first trip abroad since his election in March.

"Do not be afraid to go and to bring Christ into every area of life, to the fringes of society, even to those who seem farthest away, most indifferent," the 76-year-old Argentine said as scores of people took a dip in the ocean.

Later, the pope met with Latin American bishops and urged them again to get out of their parishes and take the word of God directly to the region's slums - one of the main themes of his week-long visit.

"Bishops must be pastors, close to the people, men who love poverty, men who do not think and behave like princes. Men who are not ambitious. Men capable of watching over the flock entrusted to them," he said.

Brazil remains the world's biggest Catholic country but its flock has dwindled while Evangelical churches have boomed. Almost 65 per cent of the population was Catholic in 2010, sharply down from 92 per cent in 1970, according to the census.

Earlier, the mass included usual Bible readings but also a rousing concert with a band and choir that could have been seen in one of Brazil's many and expanding Evangelical churches.

The crowd estimate provided by the Vatican and organisers of World Youth Day, a gathering of young Catholics, was more than twice the number of people who attended a free Rolling Stones concert in 2006.

The pope announced that Krakow, Poland, the native land of late pope John Paul II, who started the World Youth Day tradition, will host the next gathering in 2016, prompting Polish pilgrims to jump up and down on the beach.

"World Youth Day was fantastic. Everybody is united in God's path. Now the pope leaves and we have to evangelise," said Andressa Pusak, 25, of Brazil, who was among the throngs who had camped out on the beach before the mass.

Francis, who will fly back to Rome in the evening, arrived in a helicopter that flew over the landmark Christ the Redeemer statue atop a peak.

He then cruised by the crowd in an open-sided popemobile, waving at the adoring throng, kissing babies and sipping mate tea from his native country handed to him by a pilgrim.

Presidents Dilma Rousseff of Brazil, Cristina Kirchner of Argentina and Evo Morales of Bolivia were on hand for the mass.

The pope had used his visit to delve into political and social troubles in Brazil and elsewhere, voicing support on Saturday for young protesters "who want to be actors of change" and urging them to use "Christian response" to their concerns.

The pope turned to familiar issues on Sunday in his first interview since he succeeded retired pope Benedict XVI, telling Cathedral Radio that family was "important, necessary for the survival of humanity."

Later, addressing thousands of World Youth Day volunteers, the pope urged the young believers to ignore those "who say marriage is out of fashion" and "rebel against this culture that sees everything as temporary."

The crowd then chanted: "This is the youth of the pope!" The pope's charisma and desire to shake hands with his flock turned him into a star since he landed in Brazil on Monday. Throngs slept on the beach in a traditional World Youth Day vigil before the final mass.

"He's a man of the people. He has left behind all that pompous stuff of the Vatican," said Angela Collins, a 31-year-old Australian teacher as her Brisbane group dozed in sleeping bags around her.

The pilgrims used their time on the beach to mingle and discuss the pope's call to shake up the church. But some succumbed to the temptation of caipirinha cocktails served in beach bars.