Vatican City - Pope Francis was released from hospital on Sunday after surviving a life-threatening bout of pneumonia that kept him bedridden for weeks.

The 88-year-old left Rome's Gemelli Hospital, where he had been hospitalized since mid-February.

A frail-looking Francis earlier made his first public appearance since being hospitalized, thanking the thousands gathered outside the clinic while sitting in a wheelchair on a balcony.

The pope returned to the Vatican, where he will continue to receive medical treatment at his residence, Casa Santa Marta.

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At the age of 88, Francis is the second-oldest pontiff in history.

Francis' discharge from hospital on Sunday marks a remarkable recovery after he was twice in acute danger during his five weeks in hospital.

The pope first contracted bronchitis before Christmas and was forced to seek treatment at the Gemelli Hospital in western Rome on February 14. He suffered with severe pneumonia in both lungs, an infection in his respiratory tract and problems with his kidney.

News of his imminent release came as a surprise on Saturday, with doctors explaining that Francis was hoping for a speedy return to the Vatican after his state of health improved.

It is uncertain whether the Argentinian will be able to take part in Easter celebrations next month.

Doctors have recommended at least two more months of rest and advised Francis to avoid crowds due to his compromised respiratory system.

In his Angelus prayer published Sunday, the pontiff urged an end to Israel's renewed mass killings in and destruction of Gaza, saying: "I ask that the weapons be silenced immediately and that the courage be found to resume dialogue so that all the hostages can be freed and a definitive ceasefire reached."