The bells of St Peter's tolled as his body was transferred from the Vatican hotel where he lived into the basilica.
The Vatican has opened St Peter's Basilica to the general public to pay their final respects to Pope Francis, with thousands of people filling the central aisle and Swiss Guards standing at attention.
Francis died on Monday at age 88 and his body will lie in state in the basilica until Saturday's funeral and burial.
The bells of St Peter's tolled earlier today as his body was transferred from the Vatican hotel where he lived into the basilica, escorted by a procession of solemn cardinals and Swiss Guards through the same piazza where the pontiff had greeted the faithful from his popemobile just days before in what became his final good-bye.
READ MORE: Pope Francis was a source of controversy and spiritual guidance in his Argentine homeland
Pallbearers carried the simple wooden coffin on their shoulders through the Vatican's archway gates, out into St Peter's Square and into the basilica, the cardinals in their scarlet cassocks, bishops in their purple robes and the Swiss Guards in their golden and blue uniforms processing slowly behind.
Cardinal Kevin Farrell, who is running the Vatican temporarily until a new pope is elected, led the procession, with clouds of incense preceding him as the church choir began chanting the Litany of Saints hymn. In pairs, the cardinals approached the casket, bowed and made a sign of the cross, followed by small groups of bishops, ushers, priests and nuns.
Heads of state are expected for Francis' funeral on Saturday, but the three days of public viewing in the basilica will allow ordinary Catholics to grieve the 88-year-old pope, who died on Monday after suffering a stroke.
The basilica was being kept open until midnight to accommodate the crowds, a mourning period that will end on Friday at 7pm (3am Saturday AEST), when Francis' casket is closed and sealed.
Mourners in the piazza watched as Francis' casket passed them by, along the same path the pope had travelled just days before, on Easter Sunday, in what became his final popemobile tour through the faithful. It was a surprise salute, which Francis decided at the last minute after being assured by his nurse he could do it despite his continued frail health from pneumonia.
Simplified rituals reflect Francis' wishes
Francis' death and funeral inaugurates a carefully orchestrated period of transition in the 1.4-billion strong Catholic Church, with cardinals gathering over the coming week before entering into a conclave, the secretive ritual voting in the Sistine Chapel to elect a new pope. There are 135 cardinals under age 80 and eligible to vote in the conclave, and the new pontiff will likely come from within their ranks. The conclave is not expected to begin before May 5.
Francis first lay in state in the Domus Santa Marta hotel in a private viewing for Vatican residents and the papal household. Images released by the Vatican on Tuesday showed Francis lying in an open casket, wearing the traditional pointed headdress of bishops and red robes, his hands folded over a rosary. The Vatican's No.2, Cardinal Pietro Parolin, was pictured praying by Francis.
Once inside the basilica, Francis' casket wasn't put on an elevated bier — as was the case with past popes — but was just placed on an inclined ramp the main altar of the 16th-century basilica, facing the pews, with four Swiss Guards standing at attention by its side. It was in keeping with Francis' own wishes for all the rituals surrounding a papal funeral to be simplified and reflect the pope's role as a simple pastor, not a world leader.
"Look kindly, Lord, on the life and works of your servant, our Pope Francis," Farrell said from the altar.
"Welcome him into the dwelling of perpetual light and peace and grant that your faithful people may follow fervently in his footsteps, bearing witness to the Gospel of Jesus."
Italian police have tightened security for the viewing and the funeral, carrying out foot and horse patrols around the Vatican, where pilgrims continued to arrive for the Holy Year celebrations that Francis opened in December. The faithful who walk through St Peter's Holy Door are granted indulgences, a way to help atone for sins.
"For me, Pope Francis represents a great pastor, as well as a great friend to all of us,'' said Micale Sales, visiting St Peter's Basilica from Brazil.
"I think he spread a positive message around the world, saying there shouldn't be any violence, there should be peace around the world,'' said Amit Kukreja, from Australia.
Planning for the conclave is now under way
The funeral has been set for Saturday at 10am (6pm AEST) in St Peter's Square, and will be attended by leaders including US President Donald Trump and Ukrainian President Volodmyr Zelenskyy.
Cardinals are continuing their meetings this week to plan the conclave to elect Francis' successor, make other decisions about running the Catholic Church as world leaders and the ordinary faithful grieve the pontiff's death.
History's first Latin American pontiff charmed the world with his humble style and concern for the poor but alienated many conservatives with critiques of capitalism and climate change.
He last appeared in public on Sunday with an Easter blessing and popemobile tour through a cheering crowd in St Peter's Square.
He had some reservations about looping through the square packed with 50,000 faithful, Vatican News reported on Tuesday, but overcame them — and was thankful that he had greeted the crowd. He died the next morning.
"The death of a pope is not a small thing, because we've lost our leader,'' said Julio Henrique from Brazil.
"But still, in a few days, we will have a new leader. So … the thing of hope remains. Who will assume Peter's throne?"
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