Vatican City (AFP)
Pope Francis's modest tomb drew massive queues on the first day of public viewing in Rome on Sunday, a day after an estimated 400,000 people turned out for his funeral and burial.
Thousands flocked to Santa Maria Maggiore Basilica -- Francis's final resting place -- in another testament to the popularity of the Argentinian, who died aged 88 on Monday.
An energetic reformer who championed the poorest and most vulnerable, Francis is credited with reinvigorating the Catholic Church's appeal with his open, welcoming stance.
All eyes turn now to the conclave, the secretive meeting of cardinals set to convene within days to elect a new pontiff.
Many of those mourning the late pope expressed anxiety as to who will be chosen to lead the Church next.
On Monday morning, cardinals will hold their fifth general meeting since the pope's death, at which they are expected to pick a date for the conclave.
Cardinal-electors at the secret vote will cast four votes per day until one candidate secures a two-thirds majority, a result broadcast to the waiting world by burning papers that emit white smoke.
Luxembourg Cardinal Jean-Claude Hollerich said last week he expected the conclave to take place on May 5 or 6 -- shortly after the nine days of papal mourning, which ends on May 4.
German Cardinal Reinhard Marx told reporters on Saturday the conclave would last just "a few days".
'Very emotional'
Francis's funeral was held in St Peter's Square in the Vatican in bright spring sunshine, a mix of solemn ceremony and an outpouring of emotion for the Church's first Latin American pope.
Francis was then buried in an alcove of Santa Maria Maggiore, his favourite Rome church, becoming the first pope in more than a century to be interred outside the Vatican.
A couple of hours after opening, the large basilica was heaving, the crowds periodically shushed over speakers.
More than 10,000 people had filed past the tomb by midday, Italian media reported.
Among the mourners were pilgrims and Catholic youth groups who had planned to attend the Sunday canonisation of Carlo Acutis, which was postponed after Francis died.
Friday to Sunday was also the Jubilee of Adolescents, one of a series of events drawing millions to Rome to celebrate the Catholic Holy year.
Many of the mourners expressed hope that the next pope would follow Francis's example, at a time of widespread global conflict and growing hard-right populism.
Cardinal Marx said the debate over the next pope was open, adding: "It's not a question of being conservative or progressive... The new pope must have a universal vision."
'Whole world present'
Italian Cardinal Pietro Parolin -- who was secretary of state under Francis and is a front-runner to become the next pope -- led a mass on Sunday morning in St Peter's Square, which drew 200,000 people according to the Vatican.
Many were part of Jubilee youth groups from across the globe.
"(Francis) would have liked to meet you, to look into your eyes and to pass among you to greet you," he told them.
"With you here, the whole world is truly present", he said, to applause.
More than 220 of the Church's 252 cardinals were at Saturday's funeral. They will gather again on Sunday afternoon at Santa Maria Maggiore to pay their respects at Francis's tomb.
Only cardinals under the age of 80 are eligible to vote in the conclave. There are 135 currently eligible -- most of whom Francis appointed himself.
Francis, a former archbishop of Buenos Aires who loved being among his flock, was a very different character to his predecessor Benedict XVI, a German theologian.
Some cardinals have admitted the weight of the responsibility that faces them in choosing a new head of the world's 1.4 billion Catholics.
"We feel very small," Hollerich said last week. "We have to make decisions for the whole Church, so we really need to pray for ourselves."