Pope Francis spent his first day as leader of 1.2 billion Catholics meeting children and commuters, praying and paying his hotel bill.

Much has been made of the 76-year-old's humility and modesty. He was previously won praise for eschewing the trappings of office for a frugal life in Buenos Aires, where he was archbishop.

Yesterday, the former Cardinal Jorge Mario Bergoglio set down his marker as he meant to go on.

On his first morning as pontiff, Francis enjoyed an unannounced early morning visit to a Roman basilica dedicated to the Virgin Mary and prayed before a Byzantine icon of the Madonna and infant Jesus.

Father Ludovico Melo, a priest who prayed alongside him, said: "He spoke to us cordially, like a father. We were given 10 minutes' advance notice that the Pope was coming."

On leaving, he then crossed the road to greet schoolchildren and commuters travelling to work.

From the basilica, he asked to go to a Rome residence for priests so that he could pick up bags left there, before he moved to a Vatican guesthouse for the conclave of cardinals that elected him – confirming that he did not expect to become pope.

The Vatican said Francis, who has a reputation for frugality, insisted on paying the bill. "He was concerned about giving a good example of what priests and bishops should do," a Vatican spokesman said.

He celebrated his first mass at the Sistine Chapel – where only 24 hours earlier his life changed dramatically upon election – and told his followers in Italian: "I would like all of us... to have the courage to walk in the presence of God."