FATIMA, Portugal - Pope Francis on Saturday officially declared as saints two young shepherds who saw an apparition of the Virgin Mary 100 years ago.

Hundreds of thousands of people, many of whom slept outdoors to hold their places, broke into applause as the leader of the world's 1.2 billion Catholics canonized siblings Francisco and Jacinta Marto.

In the homily of a huge outdoor Mass, Francis prayed that the Madonna would protect the most vulnerable members of society, "especially the sick and the disabled, prisoners and the unemployed, the poor and the abandoned".

Pinoys who have witnessed the canonization and the centennial celebration of the apparitions of Fatima felt blessed to be here.

“It’s a once in a lifetime event for us. It’s our first time witness a canonization rites and we are really devotees of the Lady of Fatima,” said Regina Canos, who brought along husband Mark and their children all the way from Singapore.

Mark said: “I think it’s very appropriate we are witnessing two children canonized and we have two children and we are hoping that our children grow up to be like them.”

Maria Larabal, a Marian devotee from London, share the same sentiment.

“I feel blessed. We were here last year during the 99 years of the apparition of Fatima,” she said.

Two huge tapestries made from century-old photographs of the children dressed in the traditional peasant garb of the times hung from the church that is now the focal point of the sanctuary visited by about seven million people each year.

The story of the Marto children has captivated Catholics ever since their first reported vision on May 13, 1917. Their first vision was of hell and a call to prayer and conversion which, if not heeded, would lead to another world war.

The second was a warning that Russia would "spread her errors" in the world if people did not turn to God.

The third secret intrigued the world for nearly three-quarters of a century, inspiring books and cults.

Only in 2000 did the Vatican reveal the third secret: a prediction of the 1981 assassination attempt on the now Saint Pope John Paul II, who survived and subsequently gave the bullet that hit him to the Bishop of Fatima.

It was later put into the crown of the statue of Fatima, and many in Portugal say the bullet was a perfect fit, providing evidence for the vision.

Francisco and Jacinta's miracle is linked to the inexplicable healing of a terrible head injury suffered by a Brazilian child, whose parents prayed to the siblings.

Francisco died in 1919 and Jacinta died a year later, both of pneumonia, when they were just 9 and 10 years old. The third sibling, Lucia, became a nun and died in 2005 at 97. - with reports from Reuters.