Pope Francis is undergoing surgery for "colon diverticulitis," Vatican spokesman Matteo Bruni told CNN on Sunday.

It comes just hours after the 84-year-old pontiff, attended the traditional Sunday Angelus prayer in St. Peter's Square.

The Holy See press office said in a statement: "This afternoon his Holiness Pope Francis went to the Gemelli hospital -- Rome -- for a scheduled surgical intervention for a symptomatic stenotic diverticulitis.

"Surgery will be carried out by professor Sergio Alfieri. At the end of the surgery a medical bulletin will be issued."

Diverticulitis is an inflammation caused when people develop small sacs in the walls of the colon. The sacs or pouches are called diverticuli.

It's usually symptomless, but can cause discomfort and, sometimes, bleeding. It's a common condition affecting more than half of adults in the US, according to the US National Institutes of Health, and is more common as people age.