Victor R. Caivano/AP Photo

RIO DE JANEIRO - The man who has become known as the "people's pope" lived up to the title today as he called on Catholics during his first foreign trip to forego selfishness and materialism in favor of charity and sacrifice.

Pope Francis delivered a speech on the fourth day of his trip during a stop at one of Rio de Janeiro's infamous slums, known as favelas. The visit to the Varghina favela, once notorious for being one of the most violent shantytowns in the city, also highlighted the security fears that have grown during this trip around a pope who thinks little of diving into large crowds and tries at every outing to be as accessible as possible.

"Everybody, according to his or her particular opportunities and responsibilities, should be able to make a personal contribution to putting an end to so many social injustices," the pope said in his speech at a packed soccer field. "The culture of selfishness and individualism that often prevails in our society is not what builds up and leads to a more habitable world…"

It was a continuation of the theme of the pope's first mass in Brazil on Wednesday in which he called on young people to reject the "ephemeral idols" of "money, success, power, pleasure" that take the place of God.

The pope arrived today in the favela to a festive atmosphere of loud music and dancing. He transferred from his simple Fiat car to the open jeep serving as his "popemobile," a notable departure from the bulletproof vehicles that predecessors John Paul II and Benedict XVI used on foreign trips. John Paul II was shot in an open jeep in 1981 as he circled the Vatican's St. Peter's Square.

Going a step farther, Pope Francis got out of the jeep to greet people on foot, even going into a home in the favela.

Varghina was "pacified" by the police in 2012, who ousted the violent gangs that roamed there. But the visit emphasized not just Pope Francis' desire to reach out to the poor - a hallmark of his young papacy and his career - but the security concerns that have themselves become a story amid this Latin American pope's visit to the most Catholic country in the world.

The fears were ignited before the pope even arrived when a homemade bomb was found at the shrine of Brazil's patron saint, Our Lady of Aparecida, just days before the pope was to visit. Then, shortly after landing in Rio, the pope's driver took a wrong turn and the little vehicle - with its windows open - was mobbed by adoring supporters reaching out to touch the pope as guards tried frantically to push them back.

"We are not worried about security. The worry is that the enthusiasm is so big that honestly it is hard to respond to so much enthusiasm," the pope's spokesman said Monday night.

Indeed, Pope Francis has shown no sign of giving up his trademark habit of hugging and kissing as many worshippers as possible, a practice that has endeared him to many of the Church's faithful.

"I think there is a greater shift towards vigor and excitement for the faith," said Megan James, 24, visiting from Texas. "I really do feel like there has been a change…I believe that with him being here that we'll see a greater shift towards humility and putting others first."

In another major test of security, this afternoon the pope will attend an event on Rio's famous Copacabana beach to welcome him to World Youth Day that will include a prayer service and musical acts, expected to draw around one million worshippers.