Tens of thousands of mourners flooded into St Peter’s Square for the funeral of Pope Francis, the champion of the poor and the Catholic Church’s first Latin American leader.

Some people waited overnight to be first in the queue for the ceremony, which will be attended by world leaders.

The Argentinian pontiff, who died on Monday aged 88, sought to steer the centuries-old church into a more inclusive direction during his 12-year papacy.

Some 250,000 people paid their respects before his coffin during its three days of lying in state at St Peter’s Basilica, and huge numbers gathered from dawn on Friday to attend his final send-off.

“He was not just the pope, he was what the definition of being human is,” said Andrea Ugalde, 39, who flew from Los Angeles to attend Saturday’s mass.

Italian and Vatican authorities have mounted a major security operation for the ceremony, with more than 50 heads of state on the guest list.

A no-fly zone is in place, fighter jets are on standby and snipers will be positioned on roofs surrounding the tiny city-state.

“We spent the whole night here in the car with the children,” said Peruvian Gabriela Lazo, 41. “We are very sorry for what happened to him because we hold a South American pope in our hearts.”

The funeral sets off the first of nine days of official Vatican mourning for Francis, who took over following the resignation of Pope Benedict XVI in 2013.

After the mourning, cardinals will gather for the conclave to elect a new pope to lead the world’s 1.4 billion Catholics.