Pope Francis has been admitted to hospital for a scheduled surgery on his large intestine, the Vatican has announced.
Officials did not reveal when the stenosis surgery would take place, but said that there would be further news when it was complete.
Only hours earlier the head of the Catholic church had greeted the crowds in St Peter's Square and delivered mass, as per his usual Sunday tradition, and told those gathered he would be visiting Hungary and Slovakia in September.
The 84-year-old is being kept at Rome's Gemelli Polyclinic, in the north east of the city and close to the Vatican.
The Vatican said Pope Francis had "symptomatic diverticular stenosis of the colon" - a narrowing in the large intestine.
The pontiff is in generally good health, but suffers from sciatica, which gives him occasional bouts of lower back pain.
He also had a lung removed as a child.
The Pope's diary was more busy than usual last week, including a mass celebration on Tuesday to honour Catholic saints Peter and Paul and presiding over a special prayer later in the week at a service for Lebanon.
He also hosted an audience with US Secretary Of State Anthony Blinken on Monday, with the Pope appearing to be in good spirits throughout his engagements.
Francis is not the first papal patient to have had surgery at the hospital, with John Paul II having a benign tumour removed in 1992.