Pope Francis struggled to pull himself free from the grasp of a woman outside the Vatican as he toured the Christmas nativity scene in St Peter's Square.

Axar.az reports citing Euronews that the pope, who was visibly angered by the encounter, slapped the woman's hand twice after she finally let go of his hand and then walked away from the crowd.

Pope Francis had been visiting St Peter's Square on Tuesday night and was greeted by huge crowds, many of which shouted 'Pope! Pope!' and 'Happy New Year' and thrust their children towards him so he could pat their heads or pinch their cheeks.

At a New Year's Eve Vespers service in St. Peter's Basilica, Francis urged people to practice more solidarity.

Since becoming pontiff in 2013, Francis has preached openness - a reform-minded agenda that has irritated a small but vocal group of ultra-conservatives in the church.

The visit to the manger scene is a tradition for the Pope.