Pope Francis celebrates his 81st birthday at the Vatican

Pope Francis celebrated his 81st birthday on Sunday at the Vatican with an extra-long pizza, a hero cake and a message urging the world - and children in particular - to join in the holiday mood and be joyful.

Pope Francis also blew out a birthday candle erected on an extra-long pizza at the Vatican to the delight of children.

He told the children at the Vatican health service, to “eat all four meters (of the pizza)”, saying it will make them grow.

Pope Francis blows out a candle on the occasion of his 81st birthday during a private audience with children the Paul VI hall at the Vatican.

Pizza for parties in Italy is often baked in long form, instead of round pies, which are meant instead for individual portions. At the Vatican, rectangular-shaped pieces of pizza were stretched end-to-end on a table and a tall, white candle stuck in the middle.

Children hold up Baby Jesus statuettes during Pope Francis’ Angelus noon prayer in St. Peter’s Square.

Later, thousands of children in St. Peter's Square shouted birthday wishes to Francis. He replied from his window overlooking the square: "Thanks a lot, thanks a lot." His birthday coincided with his weekly Sunday appearance to faithful.

Pope Francis, framed by Christmas ornaments, delivers his message during the Angelus noon prayer.

"Be always joyful, even when things don't go as we wish they would," the pope said during the Angelus prayer.

He had earlier stressed the importance of sheltering children from adult woes.

"When children see problems at home, parents that fight, they suffer. Don't make them sad. They must always grow up with joy," he said as he met disadvantaged youngsters looked after by a Vatican foundation.

Faithful hold placards reading “Best Wishes Her Holiness” on the occasion of Pope Francis’ 81 birthday prior to the start of the Angelus noon prayer in St. Peter’s Square.

The Argentine pontiff also thanked the crowds gathered for the Angelus prayer as they sang happy birthday, and was expected to slice into his birthday cake after lunch.

Pope Francis waves to faithful prior to the start of the Angelus noon prayer.

His birthday cake sports a picture of the pope carrying the world on his shoulders, designed by Italian graffiti artist MauPal.

The artist - whose real name is Mauro Pallotta - famously depicted Francis as Superman in 2014 and has since begun supporting Vatican charitable projects by selling T-shirts bearing the flying pope.

The pear and cinnamon delight shows Francis in his white cassock, carried the globe on his back helped with one arm. The globe, divided in two but stitched back together, symbols the pope's unifying force, Rome pastry maker Hedera said.

Pope Francis received a cake for his birthday decorated with a drawing by Italian street artist Mauro Pallotta aka Maupal.

Francis's birthday this year falls on Gaudete Sunday, which the church marks as a moment of particular joy as celebrations for the birth of Jesus Christ approach.

(AFP & AP)