Many who know him said that Francis, driven by a sense of mission and a discipline born of his early training, essentially worked himself into the hospital.

Pope Francis "is more unwell than yesterday", the Vatican said in a statement on Saturday, adding that he had suffered a "prolonged asthma-like respiratory crisis" earlier in the day.

Doctors on Friday said the 88-year-old Francis is "not out of danger" ​and that the main threat facing him would be the onset of sepsis.