Devoted Australian Catholics are making the long pilgrimage across continents to pay a final farewell to “noble and modern” Pope Francis.

The pontiff died on Monday, aged 88, after a battle with a serious bout of double pneumonia.

His body is being held in state at St Peter’s Basilica, in Vatican City, where a funeral mass will be held on Saturday local time.

Crowds of up to 250,000 people are expected to attend including Prince William and US President Donald Trump.

Bishop Joe Caddy of the Cairns Diocese is among the devotees making the journey to Rome on Wednesday afternoon in hope of attending the late Pope’s funeral.

The bishop had pre-booked the trip to meet a group of young people from his diocese on a pilgrimage in Rome, but the religious leader’s death has changed those plans.

He said it would be an honour to farewell the Pope in person after meeting him in September when Francis appointed him as a bishop and again during the pontiff’s trip to Asia and the Pacific.

Fr Caddy recounted telling the Pope of his powerful symbolism when Indonesia’s chief Imam kissed him on the head during a visit to the Muslim-majority nation.

“He said, ‘You know what? Before we’re Muslim, before we’re Catholic, before we’re Christian, we’re human beings. We’re fellow travellers through humanity’,” Fr Caddy told AAP.

“I just thought that’s really emblematic of the man.”

The bishop hailed Pope Francis as a change-maker because of his regard for all humanity, the poor, the planet and climate change and his new approach of open listening rather than a top-down way.

Prayer services are being held across Australia in the lead-up to the pontiff’s funeral on Saturday and a papal conclave to elect his successor.

Outside St Patrick’s Cathedral in Melbourne, 23-year-old Josh said the Pope’s death was “quite a shock, especially given that on Easter Sunday he was out in public”.

“I saw him as a caring man, treating all people equal and I feel like he’s definitely changed a lot of people’s perspective,” he said.

Oliver Di Marzo, 18, said Francis confronted the church’s child sex abuse scandal head on and was “truly a noble and modern pope”.

“When my old parish priest Father Trevor texted me the news, I was on the tram home and I was just distraught,” Mr Marzo said.

“He was such a good pope. He truly represented Christ’s message – he gave to the poor, the marginalised, the needy.”

Governor-General Sam Mostyn and Australia’s top Catholic and Cardinal Mykola Bychok will attend the pontiff’s funeral in an official capacity.

The late Pope has bucked recent convention by requesting to be buried at the Basilica of Santa Maria Maggiore instead of St Peter’s Basilica where his predecessors have been laid to rest.

“He chose that because there is a particular image or icon of the Blessed Virgin Mary, where which he visits any time he travelled before and after and on other occasions,” the Apostolic Nuncio – the Pope’s representative – to Australia Archbishop Charles Balvo told ABC News.

Church rules state the conclave of cardinals to elect a new pontiff must begin between 15 and 20 days after the death.

Cardinal Bychok will be the only Australian to help choose Pope Francis’s successor.

Memorial masses will be held in Catholic cathedrals and churches across Australia in coming days, including in Brisbane where local heads of churches, political figures and community and business leaders will attend a Requiem Mass to pray for Pope Francis’ soul ahead of his funeral.

There are 5.1 million people in Australia who identify as Catholic, according to the 2021 Census, about 20 per cent of the population.

Source: AAP