Pope Francis makes brief appearance after Palm Sunday service

Pope Francis made a brief appearance in St. Peter's Square on Sunday at the end of a Palm Sunday service, greeting the crowds from his wheelchair as he continues to recover from double pneumonia.

"Happy Palm Sunday, Happy Holy Week," the pope said, before once returning inside the Vatican, stopping occasionally to talk with the faithful, including a group of delighted nuns.

Unlike last Sunday, when he made his first public appearance since being discharged from hospital three weeks ago, the pope was not receiving oxygen via a small hose under his nose.

Francis, 88, was discharged from hospital on March 23 after spending five weeks being treated for the lung infection, which his doctor later said had nearly killed him.

His medical team have urged him to take two months rest and the pope initially remained out of view after returning home. However, in a sign that he might be feeling stronger, he has made four unannounced appearances this past week, and also briefly met Britain's King Charles and Queen Camilla.

It is still not known how much he will participate in the forthcoming Holy Week - the most important week in the Church calendar which is packed with services and events.