Pope Francis' health has deteriorated over the past 24 hours, the Vatican said in a statement on Saturday, adding that he had suffered a "prolonged asthma-like respiratory crisis" and had needed 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.

The 88-year-old pontiff, who was admitted to the hospital last week, is being closely monitored by doctors as he undergoes treatment.