Pope Francis has agreed to spend up to a million euros to release a Colombian nun abducted by al-Qaeda-linked militants in Mali, said the cardinal, who revealed the pope's secret permit to a British security company to find and secure her release.

Cardinal Angelo Piccio's sudden testimony could have serious security implications for the Vatican and the Catholic Church, as it provides evidence that the pope is willing to pay a ransom to Islamist terrorists for the release of a nun.

Ransom payments are rarely or never announced, especially to prevent future kidnappings, and it is not known how much money the Vatican may pay to the militants, or if it has already been paid in the first place.