Pope Francis has cancelled official engagements for the third day in a row as he battles an apparent cold.

The 83-year-old, who lost part of a lung to a respiratory illness as a young man, has never cancelled so many official audiences or events in his seven-year papacy.

He is continuing to work from his residence at the Vatican's Santa Marta hotel and is receiving people in private, the Vatican press office said.

On Saturday, those private meetings were with the head of the Vatican's bishops' office, Francis's ambassadors to Lebanon and France and a Ukrainian archbishop.

Cancelled were his two planned official audiences - formal affairs in the Apostolic Palace where Francis would have delivered a speech and greeted a great number of people at the end.

Those were to include an audience with an international bioethics organisation and with members of the scandal-marred Legion of Christ religious order.

On Sunday, Francis is expected to leave the Vatican with top Holy See bureaucrats for a week of spiritual exercises in the Roman countryside, an annual retreat at the start of Lent.

Francis last appeared in public on Wednesday, when he was seen coughing and blowing his nose during an Ash Wednesday Mass. The following day, he cancelled a Mass across town with Roman priests and on Friday he skipped an audience with participants of a Vatican conference on artificial intelligence.

The Vatican has stressed that Francis has celebrated Mass each morning and greeted attendees at the end, and then proceeded to continue working from home.

The Vatican has not revealed the nature of Francis's illness, saying only he has a "slight indisposition".

It comes amid general alarm in Italy over the coronavirus outbreak, which has infected more than 800 people, mostly in northern Italy.