VATICAN CITY, April 24, 2025 (BSS/AFP) - Huge crowds were expected on Thursday for a glimpse of Pope Francis's body on the second day of public tributes, afer St Peter's Basilica stayed open almost all night to accomodate the crowds.

Close to 20,000 people filtered past the Catholic leader's red-lined wooden coffin in the first eight hours of the lying in state on Wednesday.

Instead of closing at midnight, it allowed people in until 5:30am (0330 GMT) on Thursday morning, before reopening at 7:00am, the Vatican said.

Italy is preparing a massive security operation for the funeral in front of St Peter's, with world leaders including US President Donald Trump and Ukraine's Volodymyr Zelensky due to join hundreds of thousands of mourners.

Francis died on Monday after 12 years as head of the world's 1.4 billion Catholics, during which time he made a name for himself as a pope of the marginalised.

Mourners queued for up to four hours on Wednesday to say their goodbyes to Francis, who was dressed in his papal vestments -- a red chasuble, white mitre and black shoes -- and held a rosary.

Each mourner was ushered past the casket within seconds, many hurriedly catching the moment on their smartphones.

Argentine Federico Rueda, 46, said that despite the rush, he would not have missed the opportunity.

"It is worth missing out on other places to say goodbye to an Argentine: a very worthy pope," he said as he stood proudly wearing the jersey of Argentina's national football team, the current world champions.

Mexican Leobardo Guevara, 24, draped in his country's flag, said he felt "a sense of peace" as he filed past the body of the first pope from the Americas.

- Security operation -

Francis, an energetic reformer who became pope in 2013, died on Monday aged 88 after suffering a stroke.

His death at his residence in the Casa Santa Marta in the Vatican came less than a month after he was released from five weeks in hospital with double pneumonia.

Francis's casket was initially put on display for Vatican officials and clergy in the Santa Marta chapel, before being transferred to St Peter's Wednesday in a procession including cardinals, clergy and Swiss Guards.

Italian Prime Minister Giorgia Meloni was among those who paid respects on Wednesday, and scores of world leaders and dignitaries plan to attend the funeral.

They include Argentine President Javier Milei and Britain's Prince William, although Russia -- which has for centuries had icy ties with the Vatican -- said it would send its culture minister.

Authorities, who expect up to 170 foreign delegations, have ramped up security for the funeral.

Italy's civil protection agency estimates that "several hundred thousand" people will descend on Rome on what was already set to be a busy weekend due to a public holiday.

- No conclave date yet -

After the funeral, Francis's coffin will be taken to his favourite church, Rome's papal basilica of Santa Maria Maggiore.

His will requested that he be interred in the ground, his simple tomb marked with just one word: Franciscus.

Following that, all eyes will turn to the process to choose Francis's successor.

Cardinals from around the world are returning to Rome for the conclave, which will begin no fewer than 15 days and no more than 20 days after a pope's death.

Only those under the age of 80 -- currently some 135 cardinals -- are eligible to vote.

Cardinals have agreed that the traditional nine days of mourning for the pope, the so-called "novemdiales", will begin on Saturday and conclude on May 4.

Another meeting of cardinals of all ages was set for Thursday at 9:00am (0700 GMT).

However, the Vatican brushed aside hopes of an announcement of the conclave date, insisting the focus is on the funeral.

At the time of his death, Francis was under doctors' orders to rest for two months.

But the headstrong pope continued to make public appearances despite appearing tired and short of breath.

On Easter Sunday, one day before he died, he circled St Peter's Square in his popemobile to greet the crowds, stopping to kiss babies along the way.