Pope Francis will canonize two children who claimed to have been visited by a vision of the Virgin Mary, who then predicted World War Two.

Siblings Francisco and Jacinta Marton, who said they were greeted by Mary in the Portuguese town of Fatima in 1917, will be canonized by the Pope on 13 May to mark 100 years since the alleged holy incident.

Pope Francis, who was flocked by a crowd of 1 million people when he arrived in the town 90 miles north of Lisbon, says that he wants to canonize the children to spread the message of peace to Catholics worldwide.

In a plea to the Portuguese crowds, the Pope called for "world concord among all peoples", and criticised "the bloodshed in the wars tearing our world apart."

The miracle claim, which was ratified by the Catholic Church in 1930, purports that the two shepherd children, aged nine and seven, were greeted by a vision of the Virgin Mary heralding an apocalyptic warning.

She told the two shepherd children, and their cousin Lucia Dos Santos, about the impending doom of a second world war, hell, the rise and fall of communism, and the death of a pope. In her appearance, Mary urged the illiterate children to pray for peace and turn away from sin.

Although the two siblings died two years later from a bout of influenza, their cousin spread the word of the story, and later became a nun. She died at the age of 97, and will also be beatified at the ceremony.

The Vatican secretary of state, Cardinal Pietro Parolin, said that the tale still resonates with Catholics today as it challenges the mordern narrative "of hatred, vendetta and hostilities".

The Shrine of Fatima also bore resonance for Pope John Paul II. The former Pope credited the Virgin Mary for saving his life when mercenary Mehmet Ali Ağca attempted to shoot him on Fatima's feast day in 1981 in St. Peter's Square.

The central Portuguese town receives around 7 million visitors a year to the holy shrine.