Pope Francis prays alone in the Basilica of St Mary Major
Pope Francis has warned the Catholic Church would become "a compassionate NGO" without spiritual renewal, reports the BBC.
In a Sistine Chapel Mass with cardinals on his first day as Church leader, the pontiff said: "If we do not confess to Christ, what would we be?
"We would end up a compassionate NGO. What would happen would be like when children make sand castles and then it all falls down."
Francis is the first Latin American - and the first Jesuit - Pope.
The BBC's David Willey, in Rome, says the 76-year-old has already been swift to stamp his style on the papacy. Pope Francis is regarded as a doctrinal conservative, but he is also seen as a potential force for reform of the Vatican bureaucracy, analysts say.
On Wednesday night, Pope Francis endeared himself to the crowds in St Peter's Square - and underlined his reputation for humility - when he asked them to bless him before blessing them in return from the balcony of the basilica.
The Vatican's account of his first hours in the top job on Thursday also emphasised Pope Francis's humility, describing how he shunned a special car and security detail provided to take him to the Vatican, travelling instead on a bus with the other cardinals.
Following his first outing as pope to the Rome basilica on Thursday, Francis went back to the clergy house in a city centre side street where he had been staying ahead of the conclave that elected him on Wednesday.
"He packed his bags and then he went to pay the bill for his room so as to set a good example," said Vatican spokesman Father Federico Lombardi.
Without spiritual renewal, church could become compassionate NGO (BBC)
Francis's first day as pope (Vatican Insider)