World leaders gather in Rome for Pope Francis's inauguration mass in St Peter's Square

World leaders have gathered in Rome for Pope Francis's inauguration mass in St Peter's Square, where Latin America's first pontiff will receive the formal symbols of papal power.

Hundreds of thousands of people are expected to attend the mass laden with rituals and spectacular imagery, which will begin with a tour of the famous Vatican plaza by the Argentine pope after his election last week.

Still haunted by criticism at home for failing to speak out against the excesses of Argentina's military rule, the former archbishop of Buenos Aires, Jorge Mario Bergoglio, has already won hearts in Rome with a disarmingly informal style.

Bergoglio was a surprise choice at a conclave of cardinals to replace 85-year-old Benedict XVI, who last month brought a sudden end to a papacy that had often been overshadowed by scandal, saying he was too old to carry on.

The jovial Francis has said he chose his papal name in honour of the mediaeval Italian saint St Francis of Assisi and has called for a "poor Church for the poor", warning the world's cardinals against pursuing worldly glories.

The son of an Italian emigrant railway worker from a working-class quarter of Buenos Aires has been effusive in a way that is unusual in the Vatican, kissing pilgrims and doing impromptu walkabouts.