is in a critical condition after suffering a respiratory crisis while being treated for pneumonia and a complex lung infection.

The pontiff, 88, received "high flows" of oxygen to help him breathe and was given blood transfusions after tests showed low counts of platelets, which are needed for clotting, according to the .

In a statement on Saturday, the Vatican said: "The Holy Father's condition continues to be critical, therefore, as explained yesterday (Friday), the pope is not out of danger."

It was the first time "critical" had been used in a written statement to describe Francis's condition since he was hospitalised on February 14.

The statement also said the pope "continues to be alert and spent the day in an armchair although in more pain than yesterday". Doctors declined to offer a prognosis, saying it was "reserved".

Doctors have said Francis's condition is touch-and-go, given his age, fragility and pre-existing lung disease.

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