Security was high Wednesday as groups of cheerful young pilgrims from around the globe gathered in the streets of Krakow, in southern Poland, just hours before Pope Francis arrives to join World Youth Day, a major gathering of Catholics.

A shadow was cast on the celebrations by the brutal slaying a day earlier of a priest in France, adding to security fears already high due to a string of violent attacks in France and Germany. Polish officials said they have deployed tens of thousands of security officials to cover the event, which runs through Sunday.

"It shocked me because it seems they waited for the time of World Youth Day to attack us Catholics," said Nounella Blanchedent, 22, from the French Caribbean island of Guadeloupe. "They chose the time of such a mass event to gather more attention to what they do. It's a pity because all that we want to do is to be together, sing and praise God. And they want to disturb that. It's a disaster."

She was one of the volunteers helping with security and logistics at the packed St. Casimir Church, where a Mass was being held in French for pilgrims from France, Belgium and other countries.

Relics of St. Mary Magdalene came to the church from France, for the duration of World Youth Day, and were displayed in a case by the altar.

"Their presence helps us concentrate on our prayers and brings us closer to God," a smiling Blanchedent said.

Francis is arriving on his first visit to Poland, a predominantly Catholic country that is still proud of the late pontiff, St. John Paul II, who served as priest and archbishop in Krakow before becoming pope.

The sense of expectation was apparent in sunny Krakow on Wednesday with papal white-and-yellow flags and images of Francis and John Paul II decorating the streets. Stages were put up at many locations for concerts and other activities that are being held by and for the pilgrims in Krakow.

There was a heavy presence of police and other security forces across the city, as crowds were increasing everywhere.

"I have never seen so many people in Krakow, it's difficult to move around even though offices have closed (for the event) and many people have left the city," said Anna Gazda, 43, owner of a souvenir shop.

The weather forecast for Krakow said rainstorms were possible later in the day.

Some 200,000 pilgrims attended an inaugural Mass Tuesday afternoon.