South Korea will host the next World Youth Day, a major Catholic youth festival, in 2027, Pope Francis said on Sunday at the close of this year's event in Lisbon.

"The next World Youth Day will be in Asia. It will be in South Korea in Seoul," the pontiff told the faithful assembled to celebrate a mass at a park on the eastern outskirts of the Portuguese capital.

"And so in 2027, from the western border of Europe it will move to the Far East, and this is a beautiful sign of the universality of the Church."

The crowd of around 1.5 million flag-waving young pilgrims from around the world cheered at the announcement.

The festival has only been held in Asia once -- in the Filippino capital Manila in 1995.

World Youth Day, which is in fact a week-long Catholic jamboree, features a wide range of events, including concerts and prayer sessions.

"We believe visitors to Korea will be impressed by our country's remarkable efficiency," the Archbishop of Seoul, Peter Soon-taek Chung, told a news conference in Lisbon after the pope's announcement.

"The World Youth Day is not just a Catholic event. It is a global celebration and a platform for inter-religious encounters," he added.

This year's festival, initially scheduled for August 2022 but postponed because of the Covid-19 pandemic, was the fourth for Francis after Rio de Janeiro in 2013, Krakow in 2016 and Panama in 2019.

Created in 1986 by John Paul II, it is an opportunity for the Vatican to galvanise young Catholics at a time when secularism and priest paedophilia scandals are causing some to abandon the faith.

Pope Francis visited South Korea in 2014, in what was the first trip to Asia by a pontiff in 15 years.

The country is one of Roman Catholicism’s few strongholds in Asia.

About 11 percent of South Korea's population of around 52 million people are Catholic, a number that has increased in recent decades.