Warning that “the pope is not out of danger”, the statement marked the first time the Vatican has described Francis’s condition as “critical” after his health deteriorated over the past 24 hours.
It came after the Vatican issued an unusual and official denial of an Italian media report that said Cardinal Parolin and the Pope's chief canonist had visited Francis in the hospital in secret.
Pope Francis is in a critical condition after he suffered a long asthmatic respiratory crisis that required high flows of oxygen, the Vatican has said.
Dr Sergio Alfieri, the head of medicine and surgery at Rome's Gemelli hospital, said the biggest threat facing Francis was that some of the germs that are currently located in his respiratory system pass into the bloodstream, causing sepsis.
The Vatican secretary of state, Cardinal Pietro Parolin, who is sometimes referred to as the deputy pope, gave a rare interview to Italian newspaper Corriere della Sera to respond to the rumours.