Well-wishers in the crowd waved US and Peruvian flags, with people from both countries claiming him as the first pope from their nations.

The open-topped popemobile was surrounded by more than a dozen security guards as it drove through the square and down the long boulevard that leads to the Tiber River, for Pope Leo’s first ride. Source: AP / Andrew Medichini

Born in Chicago, the 69-year-old pontiff spent many years as a missionary in Peru and also has Peruvian citizenship.

Crowds chanted “Viva il Papa” (Long Live the Pope) and “Papa Leone”, his name in Italian, as his distinctive, open-topped popemobile weaved around St Peter’s Square.

The vehicle moved quickly, but briefly stopped twice so Leo could bless three babies. Source: AP / Andrew Medichini

Robert Prevost, a relative unknown on the world stage who only became a cardinal two years ago, was elected pope on 8 May after a short conclave of cardinals that lasted barely 24 hours.

Francis, an Argentine, died on 21 April after leading the Church for 12 often turbulent years during which he battled with traditionalists and championed the poor and marginalised.

Italian authorities deployed thousands of security officers for the event, alongside snipers on rooftops and anti-drone operations. Source: Getty / Picture Alliance

In his sermon, read in fluent Italian, Leo said that as leader of the world’s 1.4 billion Roman Catholics, he would not shrink before modern challenges and that, at least on social issues such as combating poverty and protecting the environment, he would continue the legacy of Pope Francis.

Referring to St Peter, the 1st century Christian apostle from whom popes derive their authority, Leo said: “Peter must shepherd the flock without ever yielding to the temptation to be an autocrat, lording it over those entrusted to him. On the contrary, he is called to serve the faith of his brothers and sisters, and to walk alongside them.”

US Vice President JD Vance, a Catholic convert who clashed with Francis over the Trump administration’s hard-line immigration policies, led a US delegation alongside Secretary of State Marco Rubio, who is also Catholic.

US Vice President JD Vance briefly shook hands with Ukrainian President Volodymyr Zelenskyy at the start of the inauguration ceremony. Zelenskyy last met Vance in February in the White House, when the two men clashed fiercely in front of the world’s media. Source: AP / Gregorio Borgia

of the inauguration in the Holy See.

European royals also took their place in the VIP seats near the main altar, including Spanish King Felipe and Queen Letizia.