The pontiff left the hospital on Sunday following treatment for a severe respiratory infection that led to bilateral pneumonia.

The 88-year-old pontiff is responding well to the treatment for double pneumonia and has shown a "gradual, slight improvement" in recent days, the Vatican said Saturday.

Pope Francis experienced more respiratory problems and went on noninvasive ventilation on Monday, the Vatican said, as the head of the Roman Catholic Church battles double pneumonia in the hospital.

The Vatican says Pope Francis's condition has worsened after a breathing crisis in hospital on Friday - two weeks after he was first admitted to hospital in Rome with bronchitis.

Francis, 88, has been in critical condition for several days and he has remained absent from several regular appearances. The church has encouraged worshippers around the world to pray for his health.

Pope Francis' condition remains critical but stable and he was able to do some work while still in the hospital with double pneumonia, the Vatican said in a Tuesday evening update.

Francis, 88, had remained in critical condition throughout the weekend after severe breathing difficulties were reported.

Pope Francis has pneumonia in both lungs, according to the Vatican. There's concern about the ability of the 88-year-old pontiff to fight off the infection.

Even while Pope Francis is hospitalized, he still keeps in touch with a Roman Catholic parish in Gaza City, making near-nightly phone calls to the priest and congregation there.

The 88-year-old pontiff was initially admitted to the hospital on Friday for bronchitis. On Monday, the Vatican said test results show Francis has "a polymicrobial infection of the respiratory tract."

Doctors prescribed "absolute rest" for Pope Francis, the Vatican said Saturday, a day after the 88-year-old pope was admitted to a hospital following a weeklong bout of bronchitis.

In a strongly worded letter to Catholic bishops in the United States, Pope Francis is taking to task the Trump administration's stance on migrants, calling it a "major crisis."

President Biden notified Congress of his intent to lift the U.S. label of Cuba as a state sponsor of terrorism as part of a deal aided by the Catholic Church to free political prisoners on the island.

In Pope Francis' autobiography Hope he reiterates themes of his papacy like hatred of war and unchecked capitalism, and a desire for the Catholic Church to be seen as a field hospital, not a fortress.

Pope Francis in his traditional Christmas message urged "all people of all nations" to find courage "to silence the sounds of arms and overcome divisions" plaguing the world, from the Middle East to Ukraine, Africa to Asia.