The story of Fatima's shepherd children has captivated Catholics since their first reported vision on May 13, 1917.
The Church believes the Madonna gave three children — Francisco and Jacinta Marto and their older cousin Lucia Dos Santos — three messages, the so-called secrets of Fatima. Dos Santos became a nun and died in 2005 at the age of 97, and efforts are also under way to make her a saint.
The first two secrets were revealed soon and concerned a vision of hell, seen by believers as a prediction of the outbreak of World War II, a warning that Russia would "spread her errors" in the world, and a need for general conversion to God and prayer, Reuters reported.
The "third secret" intrigued the world for more than three-quarters of a century, inspiring books and cults convinced that it predicted the end of the world.
In 2000, the Vatican said it was a prediction of the 1981 assassination attempt on Pope John Paul II on May 13, the same day of the first reported apparition in 1917.
John Paul believed the Madonna had diverted one of the bullets that hit him from his vital organs. He donated it to the sanctuary, where it is now embedded in the crown of the statue of the Madonna.