A huge billboard raising awareness of sexual abuse by clergymen was put up overnight in Lisbon, just hours before Pope Francis was due to arrive in the Portuguese capital for the world’s largest gathering of young Catholics.

The World Youth Day event was devised by the late Pope John Paul II for Catholics in their teens or early 20s and is held every two or three years in a different city.

The event comes less than six months after a report by a Portuguese commission said at least 4,815 minors were sexually abused by clergy – mostly priests – over seven decades. The commission in charge said that was just the “tip of the iceberg”.

Francis, who will be in Portugal until Aug. 6, is expected to meet privately with abuse victims.

The billboard was put up on the Almirante Reis avenue – one of Lisbon’s longest and busiest streets – and reads: “4,800+ children abused by the Catholic Church in Portugal”.

It also has 4,815 dots representing each victim.

“Nothing can repair the experience and lives of these more than 4,800 victims,” the group that organised the awareness campaign, called This Is Our Memorial, said on its website. “What we can and should do is remember them. Give them a voice. So that what happened never happens again.”

The Church had promised a memorial would be unveiled during the week-long event, but a date has not been set, with the Church saying the project was still being studied.

Lisbon Patriarch Manuel Clemente said on Monday the Portuguese church’s commitment to tackle clergy sexual abuse was “total”.

Two other billboards were put up in the nearby municipalities of Loures and Oeiras, where events related to World Youth Day will also take place.