Pope Francis slaps the hand of a woman who grabbed him at Saint Peter's Square at the Vatican. Reuters

A visibly indignant Pope Francis had to pull himself away from a woman in a crowd in St Peter's Square on Tuesday after she grabbed his hand and yanked him towards her.

Pope Francis confessed on Wednesday he had "lost patience" with an exuberant admirer who had grabbed his hand on Saint Peter's Square, prompting a swift pair of slaps.

"We lose patience many times. It happens to me too. I apologise for the bad example given yesterday," the head of the Catholic church said before celebrating Mass at the Vatican.

Pope Francis was walking through the square in Vatican City and greeting pilgrims on his way to see the large Nativity scene set up in the huge, cobbled esplanade.

After reaching out to touch a child, the Pope turned away from the crowd only for a nearby woman to seize his hand and pull her towards him. The abrupt gesture appeared to cause him pain and Francis swiftly wrenched his hand free.

The woman had made the sign of the cross as the Pope had approached. It was not clear what she was saying as she subsequently tugged him towards her.

Reuters