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.

His address, read out, condemned "worrisome" anti-Semitism, and the "deplorable" situation in Gaza.

Given his delicate health following treatment for pneumonia, it had not been certain whether the leader of the world's 1.4 billion Catholics would be present, or if so, in what capacity.

In the end, the pope made his appearance.

Francis was released from hospital on March 23, after five weeks of treatment for pneumonia, from which he nearly died.

His voice remains weak, despite improvements in his breathing. In the last week, Francis has appeared in public twice without the nasal cannula through which he has been receiving oxygen.

Pope Francis made a surprise tour of St Peter's Square in his pope-mobile for Easter Sunday, following the delivery of his address. (AFP)