Baku, August 1, AZERTAC

The world's largest Catholic gathering, a week-long religious festival known as World Youth Day, kicks off in Lisbon on Tuesday, a day before Pope Francis arrives on his first foreign trip since recent surgery, according to Yahoo News.

Around 300,000 people are expected to attend the opening mass at 7:00 pm (1800 GMT) at the hillside Eduardo VII park, which offers sweeping views of the Portuguese capital and the Tagus river.

Pilgrims roamed around Lisbon ahead of the mass, waving national flags in the air and singing Catholic anthems from their home countries.

"It's going to be extraordinary, all this Christian youth coming together," said Gabriel Forestier, a 28-year-old engineer from Amiens in northern France.

Francis is set to arrive in Lisbon on Wednesday morning to celebrate World Youth Day, which is actually a week of religious, cultural and festive events held about every three years in a different city.

The 86-year-old pontiff is by Church standards the most liberal pope in decades and is very popular with young people.

During his papacy, Francis has tried to create a more compassionate church, reaching out to the gay community and talking frankly to youngsters about abortion, divorce and gender identity.

In Portugal, he has a typically packed schedule for his five-day visit, despite having spent nine nights in hospital after undergoing hernia surgery in June.

Francis, the first Latin American pope, is due to make 11 public pronouncements and hold numerous meetings, and on Saturday will visit the shrine of Fatima north of Lisbon.

Church organisers expect one million faithful will attend the event's closing mass held by the pope on Sunday at a waterside park on the outskirts of Lisbon.

Images of the pope were on display on banners set up across the city as well as on screens on automatic bank machines along with the message: "I am with you".

A Lisbon pastry shop is even selling cookies with the image of the smiling pontiff wearing a crucifix.

"I think it is going to be an amazing experience to be in the same spot as the pope," said Barbara Weisz, a 19-year-old student from the United States, part of a group of 37 youths who came from a San Diego parish.

"It is a great feeling to be among so many young people who share your beliefs," she added as the group, who wore matching red t-shirts, gathered in the lobby of their hotel before going sightseeing before attending the opening mass.

World Youth Day, which has been dubbed the "Catholic Woodstock", is part of the Vatican's efforts to galvanise young Catholics at a time when secularism and disgust over clerical child sex abuse cause some faithful to abandon the Church.

Pope Francis is expected during his visit to meet privately with victims of sexual abuse by members of the Portuguese clergy.

A report published in February by an independent commission found at least 4,815 children were sexually abused by clergy members -- mostly priests -- since 1950.

The inquiry, based on testimony from over 500 victims, concluded that the Church hierarchy in Portugal "systematically" tried to conceal the abuse.

"I know (the meeting) will take place... but I don't know where it will happen or how many people will take part," Lisbon's patriarch, Cardinal Manuel Clemente, told a news conference Monday.

"There is a total commitment on the part of the Portuguese Church to settle this issue," he added.

Around 16,000 members of law enforcement, civil protection and medical staff are being deployed for the pope's visit, officials said.

Initially scheduled for August 2022, but postponed due to the coronavirus pandemic, the Lisbon World Youth Day is the 16th international edition of what has become the largest gathering of Catholics worldwide.

The brainchild of late Pope John Paul II that started in 1986, this year's event is the fourth presided over by Pope Francis, who became head of the Catholic Church in 2013.

The last three events took place in Rio de Janeiro, Brazil in 2013, Krakow, Poland in 2016 and Panama City, Panama in 2019.