Lisbon, May 13 (IANS): Pope Francis led a crowd of over 300,000 people in prayer before the image of Our Lady of Fatima on the eve of the 100th anniversary of the appearance of the Virgin Mary to a pair of young siblings in Portugal.

Looking out on a plaza illuminated by hundreds of thousands of candles, the Argentine pontiff on Friday evening delivered a benediction and a message in Portuguese, Efe news reported.

He then stood silently for nearly 10 minutes, gazing at the image of Our Lady, before taking a seat and, with head bowed, praying the Rosary along with the faithful gathered in Fatima for the centenary.

Many of the pilgrims planned to spend the night on the plaza to await Mass on Saturday morning.

The pope will officiate at Saturday's Mass for the canonization of seven-year-old Jacinta Marto and her brother Francisco, nine, who said that the Virgin Mary had appeared to them on May 13, 1917.

The siblings died a few years later, but their cousin, Lucia dos Santos, who was 10 at the time of the apparitions, became a nun at 14 and committed to writing the "three secrets" Mary conveyed to the children.

While the legend of Fatima remains shrouded in mystery, the Catholic Church holds that the apparition shared with the children apocalyptic visions and prophecies encompassing World War I, World War II, and the 1981 attempt on the life of Pope John Paul II.