Pontiff suffers further setback as he enters third week in hospital.

Pope Francis, battling double pneumonia in Rome's Gemelli Hospital, suffered two episodes of "acute respiratory insufficiency" on Monday, the Vatican said in its latest bulletin.

The episodes were caused by "a significant accumulation of endobronchial mucus  and consequent bronchospasm", the Vatican said on Monday evening, requiring the 88-year-old pontiff to undergo two separate bronchoscopies.

Doctors gave Francis an oxygen mask to help with his breathing, the Vatican said, noting that he "remained alert, oriented and cooperative at all times" and adding that his prognosis remains "guarded.”

Earlier on Monday the pope's condition was described as stable, after he suffered an "isolated bronchial spasm on Friday which led to a "sudden worsening" of his respiratory condition.

As Francis enters his third week in hospital, prayer vigils continue outside the Gemelli and in St Peter's Square where a Rosary is being said for the pope each night.

Photo Wanted in Rome