Pope Francis delivers his message during his weekly general audience in St. Peter's Square at the Vatican. Picture: Andrew Medichini/AP

Vatican City - The world's 1.3 billion Catholics should take some time during the month of October to pray daily for their scandal-hit church, Pope Francis said on Saturday.

"The Holy Father has decided to invite all the faithful, all over the world, to pray the Holy Rosary every day, during the entire Marian month of October," a Vatican statement said.

Prayers addressed to the Virgin Mary and Saint Michael the Archangel should seek "to protect the Church from the Devil," the statement indicated.

They should also "make it ever more aware of its guilt, mistakes, of the abuse committed in the present and the past, and committed to fight with no hesitation so that evil will not prevail."

The unusual prayer exercise is to coincide with an October 3-28 Vatican summit of world bishops, known as a synod, expected to debate recent clergy sex abuse and cover-up scandals.

They have surfaced in several countries, including in the United States, Germany, Chile and the Netherlands, throwing Francis' papacy in a deep crisis.

Last month, Francis faced an unprecedented call to resign from a former Vatican ambassador to the US, who accused him of shielding from punishment an ex-cardinal suspected of sexual misconduct.

The pope has refused to respond to Archbishop Carlo Maria Vigano, who provided no evidence for his accusations. Some see Vigano as part of a malicious conservative attack on Francis and his reforms.