A noticeably frail Pope Francis has made a surprise appearance at Vatican City. 

The 88-year-old was in a wheelchair and wearing a nasal cannula for oxygen, when greeting onlookers in St Peter's Square. 

It's his first official public appearance since he was released from hospital, after a life-threatening bout of double pneumonia. 

International Correspondent, Gavin Grey says told Andrew Dickens the Pope ignored doctor's orders. 

He says Pope Francis was told to take several weeks off duties, upon release from hospital after a five-week stay.