VATICAN CITY — Pope Benedict XVI created three new saints of the Catholic Church on Sunday in recognition of their missionary and social work with a canonisation mass in St Peter's Square.

"Christians can show the world God's love by loving their neighbour. Today, the Church shows its members three new saints who let themselves be transformed by divine charity," the pope said before throngs of pilgrims filling the sun-drenched square.

All three founded religious orders -- two Italians, Guido Maria Conforti (1865-1931) and Luigi Guanella (1842-1915), and a Spaniard, Bonifacia Rodriguez Castro (1837-1905).

Conforti was a bishop who founded the Society of San Francesco Saverio for Foreign Missions -- a congregation of missionaries known as Saveriani.

"With all his strength he dedicated himself to the good of those souls in his care, especially those who had distanced themselves from the path of the Lord," the pontiff said of Conforti, as Saveriani members looked on.

The mass was slightly disrupted when a man climbed onto a roofed area overlooking the square and set fire to a green Bible with a cigarette lighter and waved the burning pages aloft.

Security forces moved the pilgrims sitting below and persuaded the man to climb down after about half an hour.

The Vatican said he was of Romanian origin and was being questioned by police.

During the mass, as each new saint's history was read out, members of their orders prayed and a choir sang on the steps of St Peter's Basilica under huge portraits of Conforti, Guanella and Castro draped on the facade.

Guanella worked with mentally handicapped people and abandoned children and founded an organisation called the Servants of Charity.

He "brought comfort and relief to the poorest and the weakest," and shone with "God's presence and charity, the God who defended the stranger, the widow, the orphan, the poor man," Benedict said.

Rodriguez Castro, the daughter of a tailor, was also active in social causes and helped create jobs for marginalised women. She founded the Congregation of Servants of Saint Joseph.

"From a young age Saint Bonifacia knew how to honour Jesus Christ in her daily work. ... The Servants of Saint Joseph were born out of humility and the simplicity of the Gospel," the pontiff said.

Benedict has created 34 saints since the beginning of his pontificate in 2005 -- a far lower rate than his predecessor John Paul II.