The Vatican said on Saturday that Pope Francis' health had deteriorated over the past 24 hours and for the first time described his condition as "critical", reporting he had needed supplemental oxygen and blood transfusions.

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.

Pope Francis's condition "continues to be critical", the Vatican said Saturday, saying the 88-year-old was alert but had suffered a respiratory attack that required "high-flow oxygen", and also blood transfusions.