Pope Francis embarked Thursday on a ground-breaking papacy as the first Latin American leader of the world's 1.2 billion Catholics and a Church in turmoil.
Jorge Mario Bergoglio of Argentina, the humble 76-year-old son of a railwayman, kicked off his first full day as pontiff with private prayers at a Rome basilica.
The election of the former archbishop of Buenos Aires, who had not been considered a favourite in the run-up to this week's secret conclave, met with widespread surprise and expressions of hope for a groundswell of change for a Church dogged by scandal and internal conflict.
It was also seen as recognition of the Church's rapid growth in Latin America, which is now home to 40 percent of the world's Catholics, in contrast to its decline in Europe.
"The choice of Bergoglio shows that the Church is determined not to remain in mourning for the crisis in Europe but has opened its doors to the revitalising energy of Catholicism's biggest continent," Vatican expert Luigi Accatoli told AFP. "It is a momentous step."
The Italian daily La Repubblica, under the headline "Revolution at St Peter's", said the election of the former Jesuit priest represented a "geographic and cultural upheaval" for the Vatican.
Reactions continued to pour in from world leaders, with Australian Prime Minister Julia Gillard saying: "The election of a pope from the 'new world' is an occasion of genuinely historic proportions."
The new pontiff, the first from the Jesuit order, emerged smiling onto the balcony of St Peter's Basilica on Wednesday to cries of "Long live the pope!" from tens of thousands of pilgrims massed in the famous piazza below.
The first non-European pope in nearly 1,300 years devoted his first prayer to his predecessor Benedict XVI and called for "fraternity" among Catholics.
"It seems that my brother cardinals have gone to the ends of the earth (to find a pope)," Francis said, referring to his native Argentina, which erupted in celebrations at his appointment.
"Now, we take up this journey... A journey of fraternity, of love, of trust among us," he said.
Bergoglio, seen as a moderate conservative, had barely figured in the pre-vote speculation, although he is believed to have finished runner-up to Benedict in the 2005 election.
Presenting an image as a simple man of the people, he chose to name himself after the ascetic St Francis of Assisi.
But Bergoglio, hailed by US President Barack Obama as "a champion of the poor and the most vulnerable among us", is not without controversy.
He was criticised along with other Catholic clergy for failing to stand up to Argentina's military dictatorship of 1976-83, during which 30,000 people died or disappeared.
More recently, his opposition to gay marriage and the distribution of contraceptives has brought him into conflict with the Argentine government.
Argentine President Cristina Kirchner on Wednesday wished her compatriot "a fruitful pastoral mission".
There had been growing calls both within and outside the Church for the next pope to come from the southern hemisphere for the first time.
The Argentinian of Italian descent became the 266th pope after Benedict stunned the world in February with his decision to resign, the first to voluntarily step down in 700 years.
Benedict's eight-year reign was riven by scandals and the new pope will face immediate challenges -- chiefly stamping his authority on the Vatican machinery and trying to coax back a Catholic flock that is deserting churches across the West.
The hushed-up sexual abuse of children by paedophile priests going back decades cast a dark shadow over the conclave, which included several cardinals implicated in the scandals.
After Francis visited Rome's Santa Maria Maggiore basilica Thursday, a priest there told AFP: "It was a moving encounter, full of goodness and humility."
Father Ludovico Melo added that the new pope "kept telling us, 'be merciful, be merciful'."
In the late afternoon Francis will return to the Sistine Chapel, the hallowed venue of the conclave that elected him on Wednesday, to co-celebrate mass with his former peers.
The Vatican said Francis's inauguration mass would take place on Tuesday -- a significant date in the Catholic calendar because it is the Feast of St Joseph, patron saint of the universal Church.
Benedict, 85, will retire to a former nunnery inside the Vatican. Francis has already called his predecessor and they will meet soon, the Vatican said.
In one of his last acts as pope, Benedict issued a decree allowing cardinals to bring forward the date of a conclave in the event of a pope's resignation -- a move seen by many as potentially setting a precedent for ageing pontiffs in the future.
Vatican experts said the prospect of future resignations could have encouraged the cardinals to elect an older candidate in the knowledge that he could step down if his health fails.