Rome (AFP) – Pope Leo XIV presided over a final mass in Rome for over one million young people on Sunday, the culmination of a youth pilgrimage that has drawn Catholics from across the world.

"Aspire to great things, to holiness, wherever you are. Do not settle for less," Pope Leo told the young people during his homily.

The week-long pilgrimage ending Sunday, a highlight of the Jubilee holy year, was an enormous undertaking for the Vatican, with a half a million young pilgrims in Rome for most of the week.

On Saturday night, before an twilight vigil led by the pope, organisers had confirmed the attendance of 800,000 people in the vast, open-air space on Rome's eastern outskirts, and on Sunday the Vatican said that number had grown to one million people.

Most of those attending slept on the ground overnight in tents, in sleeping bags or or mats in anticipation of Sunday's mass.

In his homily, the first American pope and former missionary encouraged the gathered youth to "spread your enthusiasm and the witness of your faith to everyone you meet!"

The Vatican has sought to highlight pilgrims who managed to travel to Rome from war-torn regions, with Leo saying Sunday the Church and world's youth were with them in solidarity.

"We are closer than ever to young people who suffer the most serious evils which are caused by other human beings," he said in his Angelus, speaking in English.

"We are with the young people of Gaza. We are with the young people of Ukraine, with those of every land bloodied by war," said the pontiff, 69.

"My young brothers and sisters, you are the sign that a different world is possible, a world of fraternity and friendship where conflicts are not resolved with weapons but with dialogue."

The colourful event under sunny skies was accompanied by music from a choir, and about 450 bishops and 700 priests, all in green robes. A towering cross dominated the massive golden arch covering the stage where the pope led mass.

The young pilgrims -- hailing from 146 different countries, according to the Vatican -- have filled Rome's streets since Monday, chanting, singing and waving flags of their countries.

The festive atmosphere reached its peak Saturday ahead of an evening vigil presided over by Leo, with Italian broadcaster Rai dubbing it a Catholic "Woodstock".

Hundreds of thousands of youths camped out at the dusty venue, strumming guitars or singing, others snoozing, as music blasted from the stage where a series of religious bands entertained the crowds.

Leo was greeted with deafening screams and applause after his arrival by helicopter Saturday as he toured the grounds in his popemobile, with many people running to catch a better glimpse of the new American pope.

At over 500,000 square metres (125 acres), the grounds were the size of around 70 football fields.

British student Andy Hewellyn had parked himself in front of a huge video screen -- a prime spot, as he could not even see the stage far away.

"I'm so happy to be here, even if I'm a bit far from the pope. I knew what to expect!" he told AFP.

"The main thing is that we're all together."

The youth pilgrimage came about three months after the start of Leo's papacy and 25 years after former pope John Paul II organised the last such youth gathering in Rome.

It was announced by former Pope Francis during World Youth Day in Lisbon in 2023.

The Church planned a series of events for the young pilgrims over the course of the week, including turning the Circus Maximus -- where chariot races were held in ancient Rome -- into an open-air confessional.