Pope Francis, who has been battling pneumonia for two weeks, has had an "isolated" breathing crisis in hospital, the Vatican has said.

It led to an episode of vomiting and a "sudden worsening of his respiratory condition" on Friday following the coughing "bronchospasm".

The 88-year-old's lung's had to be aspirated - cleared of the vomit - and he is now receiving gas through a face mask to help him breathe. 

Vatican sources say the Pope's doctors need 24-48 hours to determine whether there has been any damage or set back to his condition. For now they are not giving any prognosis. 

The Pope remains alert and "in good spirits", the sources say.

In a statement the Vatican said: "In the early afternoon of today, after a morning spent alternating respiratory physiotherapy with prayer in the chapel, the Holy Father presented an isolated crisis of bronchospasm which, however, led to an episode of vomiting with inhalation and sudden worsening of the respiratory condition.

"The Holy Father was promptly bronchoaspirated and began non-invasive mechanical ventilation, with a good response to gas exchange."

Vatican sources said the latest crisis happened at around 14:00 local time, but did not say how long it lasted.

This latest episode comes after a couple of days in which Vatican statements had been slightly more positive, talking of a "slight improvement" in the pontiff's condition.

This morning he was given Communion. 

In an earlier medical update this morning, the Vatican had said the pontiff was showing signs of improvement and would remain in Rome's Gemelli Hospital due to the complex clinical picture. 

The Pope was admitted to hospital on 14 February after experiencing breathing difficulties for several days.

He was first treated for bronchitis before being diagnosed with pneumonia in both lungs.

Then, on 22 February, the Vatican said that the Pope had experienced a respiratory crisis and was in a "critical" condition, but later on Sunday released an update saying that he had "not presented any further respiratory crises".

The following day, the Pope issued a statement asking Catholics to pray for him after he was unable to deliver the traditional Angelus prayer in person for the second week running.

But, while the Vatican said the Pope's health is improving, it added that "further days of clinical stability are necessary to resolve the prognosis".