Pontiff hospitalised for first time since his election in 2013.

Pope Francis has "responded well" to colon surgery at Gemelli hospital in Rome, according to a statement released by the Vatican just before midnight last night.

The 84-year-old pope underwent surgery for a diverticular stenosis of the colon, with the Vatican underlining that the operation was scheduled and not the result of an emergency - despite taking the world by surprise.

Diverticular disease is a condition that involves bulges or sacs forming in the wall of the large intestine, with symptoms include bloating, recurrent abdominal pain and changes in bowel habits.

It is the first time that the pontiff has been hospitalised since his election in 2013, apart from a cataract operation a couple of years ago.

The Holy See press office gave no indication of how long the pope would remain in hospital but Italian news agency ANSA reported that it would likely be "at least five days."

The pope was admitted to the Gemelli in the afternoon, after the Sunday Angelus in St Peter's Square, reportedly without any fuss and accompanied by just his driver and an aide.

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With the exception of senior management and the surgeons directly involved, neither medical staff nor patients at the Gemelli were aware of the arrival of the pope, according to ANSA.

The three-hour surgical operation - carried out by a 10-person medical team led by Dr Sergio Alfieri - appears to have been timed to coincide with the pope's annual summer break from the weekly general audiences and private audiences.

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The decision to undergo surgery is believed to have been taken after the appointment of the pope's new personal doctor, Roberto Bernabei, who assumed his role in February.

Francis is being treated on the 10th floor of the Gemelli, in a section reserved exclusively for popes, in the same ward that hosted Pope John Paul II after he was shot in 1981.

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Earlier this year Pope Francis - who had part of one lung removed in his 20s - missed several New Year ceremonies due to sciatica, a painful nerve condition.

Messages of support and wishes for a speedy recovery have been flowing in for the pope from around the world, including from Italy's president Sergio Mattarella and Rome mayor Virginia Raggi, on behalf of Romans who wish their bishop well.

Rivolgo un pensiero a Papa Francesco da parte di tutta la città di Roma. Auguri di pronta guarigione.

— Virginia Raggi (@virginiaraggi) July 4, 2021