Outside Gemelli Hospital, which has treated several popes, a few Catholics lingered after the pontiff was admitted, wanting to remain close by.

"He seems calm, so we are calm too - even though illness is always unpleasant," Carla told the BBC. "We will wait here and pray."

"I was in St Peter's Square when he made the announcement and I felt really awful," said Elsa. She had thought he was a younger, healthier Pope, so had been "really taken aback" by the news.

Elise Ann Allen, who wrote a biography of the Pope, told the BBC that it would be "premature to be alarmed, but it's also premature to say everything's fine".

She urged others to wait to hear from his doctors before jumping to conclusions, telling the World Service's Newsday programme: "We don't know how much of a crisis it is at this point, but it's certainly a scare."

Since the Pope's diagnosis, it has emerged that his brother, Louis Prevost, was also being treated for a different kind of cancer - multiple myeloma, a type of blood cancer.

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