Photos: Pope Francis lies in state as mourners flock to Vatican City

Vatican City: Tens of thousands of mourners began saying their last goodbyes to Pope Francis at St Peter's Basilica Wednesday, as the body of the late Argentine pontiff began three days of lying in state.

A long line of pilgrims and tourists stretched across the sprawling St Peter's Square before the doors opened at 11:00 am (0900 GMT), when the public were allowed inside to file past the open coffin.

Francis, an energetic reformer who took over as leader of the world's 1.4 billion Catholics in 2013, died on Monday aged 88. He had recently been hospitalised for five weeks with pneumonia.

Dressed in his papal vestments - a red chasuble, white mitre and black shoes - and with a rosary laced between his fingers, the pope's body has been laid out in a red-lined wooden coffin.

For the next three days, it will rest on a low bier before the Altar of the Confession underneath the soaring dome painted by Michelangelo, before being closed at 8:00 pm (1800 GMT) on Friday evening ahead of Saturday's funeral.

Authorities said some 20,000 people were in line to enter the basilica when the doors opened. Inside, the crowd stood about 10 abreast, slowly advancing down the nave towards the casket.

Hours before, a procession of cardinals, clergy and Swiss Guards escorted Francis's coffin from the chapel of the Casa Santa Marta, where he lived during his 12-year papacy, to St Peter's.

Bells from the basilica rang out as the coffin was carried by pallbearers past packed crowds in St Peter's Square, who snapped photos and applauded.

Saturday's funeral is expected to draw hundreds of thousands of pilgrims, as well as world leaders including US President Donald Trump and Ukraine's Volodymyr Zelensky, as well as Britain's Prince William.

Afterwards, Francis's coffin will be taken to his favourite church, Rome's papal basilica of Santa Maria Maggiore, where it will be interred in the ground and marked by a simple inscription: Franciscus.