Pope Francis is "in good condition, alert and breathing on his own" a day after he underwent a three-hour operation, which involved removing half his colon, the Vatican said.

Vatican spokesman Matteo Bruni also said on Monday that Francis is expected to stay in Rome's Gemelli Polyclinic, a Catholic hospital, for about seven days "barring complications".

The brief medical bulletin contained the first details the Vatican released, coming more than 12 hours after the end of Sunday's surgery.

The procedure was necessitated by what the Holy See said was a diverticular stenosis, or narrowing the pope's sigmoid portion of the large intestine.

"His Holy Father is in good, general condition, alert and breathing spontaneously," Mr Bruni said in a written statement.

"The operation for the diverticular stenosis, performed during the evening of July 4, involved a left hemicolectomy and lasted for about three hours," Mr Bruni said.

That procedure entails removing the left side of the colon and attaching the remaining parts of the large intestine.

Francis was spending his first morning convalescing in a Rome hospital following the surgery on the left side of his large intestine.

Earlier, an Italian cardinal told reporters he had been informed that Francis was doing OK post-operatively.

"Our prayer and our closeness are very great," Cardinal Enrico Feroci said at Rome's airport where he was catching a flight.

The Italian news agency Ansa quoted him as saying that he had heard earlier in the morning from another cardinal, Angelo De Donatis, "and he told me that the pope is well".

Cardinal De Donatis is the vicar of the Rome diocese.

An earlier written statement, which came shortly before midnight on Sunday, was notable for its scarcity of medical detail.