Pope Francis appeared in front of thousands of Catholic faithful at St Peter's Square on Sunday for Easter, despite the 88-year-old pontiff's frail health that has kept him from most Holy Week events.

"Happy Easter," said the Argentine pontiff in a weak voice from his wheelchair at the balcony of St Peter's Basilica, to the delight of tens of thousands of faithful and others in the flower-filled square.

The pope traditionally delivers his "Urbi et Orbi" ("To the City and the World") benediction from the balcony that overlooks St Peter's Square, but he gave that task to a collaborator Sunday.