Pope Francis appealed to the Roman Catholic Church on Thursday not to forget its primary mission of proclaiming the message of Jesus Christ or risk being reduced to what he called "a compassionate NGO".
The Argentinian pope, speaking in Italian without notes in his first public Mass since his election on Wednesday, said the Church should shun worldliness and be more focused on the Gospels.
He also expressed his wishes to contribute in improving Jewish-Catholic ties.
Earlier, Pope Francis put his humility on display during his first day as pontiff, stopping by his hotel to pick up his luggage and praying like a pilgrim before a beloved shrine in a decidedly different style for the papacy usually ensconced inside the frescoed halls of the Vatican.
The former archbishop of Buenos Aires, Cardinal Jorge Bergoglio, made an early morning visit in a simple Vatican car to a Roman basilica dedicated to the Virgin Mary and prayed before an icon of the Madonna.
He had told a crowd of some 100,000 people packed in rain-soaked St. Peter's Square just after his election that he intended to pray to the Madonna "that she may watch over all of Rome."
He also told cardinals he would call on retired Pope Benedict XVI, but the Vatican said the visit wouldn't take place for a few days.
The new pope has daunting challenges ahead ranging from the church sex abuse scandal to reinvigorating the flock.
And Francis will have to do it all with just one lung.
The Argentine pontiff lost the greater part of one lung to a teenage infection. "He feels it today," says his authorized biographer Sergio Rubin. "He's a little bit slowed by it, but he's OK."
Doctors said that losing one lung doesn't necessarily compromise the pope's health or reduce his life span, though it means no strenuous exercise since he no longer has as much air capacity as people with two lungs.
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Latin America's Roman Catholics rejoiced that the new Pope Francis is one of their own, while elsewhere the world has hailed him as a humble champion of the poor and wished him the strength to lead the Church out of crisis.
Commentators said Francis had a reputation for being as conservative as his predecessor, Pope Benedict XVI, but Latin American Catholics celebrated the fact that the cardinals had, in his words, gone "to the end of the world" to find him.
"A Latino is more open to others, while a European is more closed," said 75-year-old Ana Solis outside Santiago's Metropolitan Cathedral in Chile. "A change like this will be very important for us Latin Americans."
Latin America is home to 42 percent of the world's 1.2 billion Catholics and the election of Argentinian Jorge Mario Bergoglio ended nearly 1,300 years of popes born in Europe.
The choice of papal name in tribute to the medieval Saint Francis of Assisi, known for a life of poverty and simplicity, also suggested an emphasis on humility from a man known at home for cooking his own meals and traveling by bus.
U.S. President Barack Obama called him "a champion of the poor and the most vulnerable among us".
For Protestants, whose Christian forebears broke with Rome 500 years ago, the World Communion of Reformed Churches wrote to Francis saying: "We are touched by your humility ... The name you have chosen is a sign for us that attention to the plight of the poor and justice for all people will be important for you."
Francis must tackle crises caused by child abuse by priests and the leak of secret papal documents that uncovered corruption and rivalry inside the Church - trouble that Benedict declared in February was, at age 85, beyond his physical capabilities.
Enda Kenny, the prime minister of staunchly Catholic Ireland who has accused the Vatican of hampering an inquiry into child sex abuse by Irish priests, summed up the thoughts of many:
"We pray that he will have the strength, the good health and the spiritual guidance needed to lead the Catholic Church in the many challenges it faces," Kenny said.
Francis also faces challenges from outside his Church, with the growth of Islam a particular concern in Africa and Asia, and the advance of secularism in its European heartland and beyond.
In Indonesia, home to the world's largest Muslim population, some were mindful of criticism of Islam by previous popes. Slamet Effendy Yusuf, head of the Indonesian Ulema Council, noted that most Muslims live in developing countries.
"We think that the new pope will better understand why in Islam there tends to be an attitude of negativity towards the West, because he is from a developing country himself," he said.
"I hope the new pope will ... engage more in dialogue and not confrontation. We believe this is a new chapter in the history of relations between Muslims and Catholics."
U.N. Secretary-General Ban Ki-moon said he hoped Francis would continue to promote inter-faith talks.
Russia's Orthodox Church hoped "that relations between the Orthodox and Catholic churches will develop in a positive spirit". It shares Catholics' conservative morality but disputes still strain relations nearly a millennium after the Great Schism split Christianity into eastern and western branches.
President Vladimir Putin said he was sure that "constructive interaction between Russia and the Vatican will continue to develop on the basis of the Christian values that unite us".
Venezuela's interim President Nicolas Maduro said on Wednesday that late Venezuelan leader Hugo Chavez's influence may have stretched into
the afterlife and had a hand in Christ's decision to opt for a Latin
American Pope . "We know that our commander ascended to the heights and is face-to-face with Christ," Maduro said at a Caracas book fair. "Something influenced the choice of a South American pope, someone new arrived at Christ's side and said to him: 'Well, it seems to us South America's time has come.'"
The World Jewish Congress offered congratulations and Israeli President Shimon Peres said Francis "comes in the wake of a pope who greatly promoted ties with us". He added: "I am sure that the chosen pope will maintain this course."
Some questioned whether Francis, the 76-year-old son of an Italian immigrant railway worker, was too old to lead a Church that needs to attract younger worshippers to fill emptying pews.
"I think they missed an opportunity to renew themselves: they've picked another old guy," said Daniel Villalpando, a 32-year-old web designer in Mexico City.
Even in the Philippines, the Church's bulwark against Islam in Asia, Father Francis Lucas of the Catholic Bishops' Conference said the new pope was "not young any more".
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Catholics in Africa and Asia on Thursday greeted the election of Pope Francis from Argentina as a historic breakthrough that would pump the developing world's vital energy into a struggling Church and amplify the voice of the planet's poor.
While there was disappointment that Pope Benedict's successor did not come from the African or Asian continents, Cardinal Jorge Bergoglio's Third World origins spurred hopes of a kindred spirit among Catholics from Manila to Maputo.
Argentina, in Latin America's southern cone, is as far from Africa and Asia as Europe, the prime source of previous pontiffs. But these rapidly developing southern continents of the globe, where poverty still looms large, are now home to the world's fastest growing Catholic communities.
Father Raymond Anoliefo, who runs a parish Church at Ibeju, said he was heartened to hear that Bergoglio had criticized the Argentine government for not doing enough to tackle poverty.
In the Philippines, where more than 80 percent of the population are Catholic, Church leaders saw the selection of the first non-European pontiff in well over a millennium as a just recognition that the face of global Catholicism was changing.
"Hand of God" brings Argentina pope, Maradona says
The same "hand of God" brought the papacy to Argentina as helped it to the 1986 World Cup, says Diego Maradona, the soccer legend whose famously illicit, handled goal against England still excites passions at home and abroad.
In a letter to Rome's Il Messaggero newspaper on Wednesday from his base in Dubai, Maradona, 52, described himself as a devout Roman Catholic and said he rejoiced at the election of his compatriot Cardinal Jorge Bergoglio as Pope Francis.
"I am truly very happy and I am certain that my enthusiasm is shared by the whole Argentinian people," he wrote.
"Everybody in Argentina can remember 'the hand of God' in the England match in the 1986 World Cup. Now, in my country, the 'hand of God' has brought us an Argentinian pope."
In a quarter-final tie in 1986, Maradona eliminated England with two goals, one a brilliant solo run through the defence, the other a handball that the referee mistook for a header.
He said afterwards that the goal was scored "a little with the head of Maradona, a little with the hand of God".
That remark still rankles in England, where the top-selling Sun newspaper's splash on the Argentinian pope showed Francis raising his arm in benediction with the headline: "Hand of God".
AP/REUTERS