Pope Francis has made a surprise appearance at St Peter's Square in the Vatican following his discharge from hospital after five weeks of treatment.

The Pope briefly appeared on stage in a wheelchair, with an oxygen tube under his nose.

"Hello to everybody," he said, waving to cheering crowds. "Happy Sunday to all of you, thank you very much."

The Pope, 88, was discharged from hospital in Rome on 23 March and appeared at his window then to offer a blessing.

Doctors said at the time he would need at least two months of rest at his residence. On Friday, the Vatican said his health was improving and he was "in good spirits" as he continued his work activities.

The Pope was admitted to hospital on 14 February for an infection that resulted in double pneumonia. One of his doctors said he had two critical episodes during his treatment where his "life was in danger".

As of Friday, the Pope had improved slightly in breathing, movement and speaking, the Vatican said. Recent blood tests also showed a slight improvement in his lung infection.

The Pope is requiring less supplemental oxygen, but continues to receive it during the day. At night, he receives a high-flow of oxygen through his nose as needed.

He has suffered a number of health issues throughout his life, including having part of one of his lungs removed at age 21, making him more prone to infections.

Pope Francis, who is from Argentina, has been Pope for 12 years.