Pope Francis takes part in the penitential procession on Ash Wednesday in Rome, Italy, February 26, 2020. Remo Casilli, Reuters

VATICAN CITY - Pope Francis canceled a scheduled appearance at mass in Rome on Thursday because of "a mild ailment", the Vatican said, the day after he appeared to be suffering a cold.

"Due to a mild ailment, he preferred to stay in the vicinity of Saint Martha's," the guest house at the Vatican where the 83-year old pontiff lives, chief press officer Matteo Bruni said in a statement.

The mass in question was at the Basilica of St. John Lateran, one of Rome's biggest and largest churches.

Bruni said the Argentine's schedule remained otherwise unchanged.

The announcement came as Italy struggles to control the largest outbreak of the coronavirus in Europe with some 400 cases.

The Vatican made no reference to the disease in its announcement.

Francis has not curtailed any of his activities, which often include mingling with crowds and shaking hands.

The Pontiff, who only has one lung and suffers problems with one hip, very rarely cancels an appointment in his busy schedule.

Vatican News said the Pope had earlier Thursday celebrated the daily mass at Saint Martha's House, before meeting members of a global Catholic climate movement as planned.