Pope Francis was mobbed by adoring pilgrims and greeted by a gay kiss-in as he arrived in Rio de Janeiro, Brazil on Monday.

In his first international trip, the Argentine pope will be participating in World Youth Day, a weeklong event that celebrates the contributions of young Roman Catholics.

An estimated 400,000 pilgrims from around the world have registered for the event. However, additional crowds – possibly in the millions – are expected at events which are open to the public.

“Thank you to all of you and to all the authorities for a magnificent welcome in Rio,” Francis tweeted to his nearly 3 million followers.

Activists waving rainbow flags and signs which read “In Every Kiss a Revolution” and “God is [heart] Gay” kissed their same-sex partners as the papal motorcade made its way to Rio's Guanabara Palace, where Francis met with Brazilian President Dilma Rousseff and an official welcome ceremony took place.

Joao Pedro Accioly, a 19-year-old who helped organized the so-called “LGBT Beijaco,” told Brazilian media that the goal of the protest was to undermine the influence of the Catholic Church in Brazil – which is home to 10 percent of the world's Catholics. He said gay rights are rarely discussed due to the church's influence.

A demonstration to protest sexual violence against women is expected to take place on Saturday. Brazilian women will march in suggestive nun outfits as part of a “SlutWalk.”

Francis left the Vatican just as an Italian weekly magazine accused the newly appointed “prelate” of the Vatican “bank” of being gay.

(Related: Gay scandal rocks Vatican.)