Pope Leo XIV has celebrated his first mass in the Sistine Chapel with a warning that people are ditching religion for “technology, money, success, power, or pleasure”.

Less than 24 hours after his election, the first American pontiff said he hoped the Catholic Church could be a beacon lighting the world’s “dark nights”.

Leo, the former Cardinal Robert Prevost, looked calm as he delivered the mass in the frescoed chapel with the same cardinals who chose him to be the 267th pontiff and the successor to Pope Francis.

As the world learns more about the new pope, his past criticisms of President Donald Trump and Vice-President JD Vance’s policies have surfaced.

In February, an X account of Robert Prevost reposted an article headlined, “JD Vance is wrong: Jesus doesn’t ask us to rank our love for others.”

In April, when Trump’s deportations to El Salvador were making headlines, Prevost reposted a comment: “Do you not see the suffering? Is your conscience not disturbed?”

While Trump was quick to congratulate the pope and express pride in an American’s election, MAGA supporters have reacted with dismay.

Prominent Trump activist Laura Loomer wrote on X: “He is anti-Trump, anti-MAGA, pro-open Borders, and a total Marxist like Pope Francis.”

Right-wing activist Charlie Kirk posted: “Pope Leo XIV: Registered Chicago Republican and pro-life warrior OR Open borders globalist installed to counter Trump?”

Leo, 69, who was born in Chicago but spent two decades as a missionary in Peru, said a few words in English before continuing his homily in fluent Italian.

He painted the spiritual picture of the church he would like to see under his papacy.

“God has …. entrusted this treasure to me so that, with his help, I may be its faithful administrator for the sake of the entire mystical Body of the Church,” he said on Friday.

“He has done so in order that she may be ever more fully a city set on a hill, an ark of salvation sailing through the waters of history and a beacon that illumines the dark nights of this world.”

The 1.4 billion-member church was great not because of “the magnificence of her structures or the grandeur of her buildings … but rather through the holiness of her members”, he said.

An inauguration mass for Leo will be held in St Peter’s Square on May 18, with world and religious leaders invited to attend.

Pope Francis’s inauguration in 2013 attracted a crowd estimated at 200,000 people.

Senior Vatican officials will be left in their roles for the time being, giving Leo time to decide on definitive appointments.

The Pope was elected at the end of a two-day conclave that end on Thursday evening when white smoke billowed from the chimney on the Sistine Chapel.

Given the nature of the conclaves, when cardinals are shut away from the world and sworn to secrecy, little or nothing is likely to emerge about how Leo obtained the required two-thirds majority of the vote so swiftly.

The successor to Pope Francis, who died in April at age 88, inherits a number of major challenges, ranging from a budget shortfall to divisions over whether the church should be more welcoming towards the LGBTQI community and divorcees, and should let women play a greater role in its affairs.

Before Leo’s election, US cardinals had largely been written off as papal contenders because of a widespread assumption that the global church could not be run by a superpower pope.

However, he also holds Peruvian citizenship, meaning he has deep knowledge of both the West and less developed nations.

He worked for decades in the north of Peru, first as a missionary and later as bishop of Chiclayo from 2015 to 2023.

One of the clues to what kind of a church leader Leo will be was in his choice of name.

The last pope with this name was Leo XIII, who led the church from 1878 to 1903 and was known for his focus to social justice issues.

Prevost became a cardinal only in 2023. Francis brought him to Rome two years ago to head the Vatican office in charge of choosing which priests should serve as Catholic bishops.

-with AAP