Pope Francis apologised on Wednesday for having angrily slapped a woman's arm when she had grabbed hold of his hand and yanked him towards her, saying he had lost his patience and set a "bad example".

His unusual apology came after he used his first homily of the new year to denounce violence against women, which he compared to profaning God.

Pope Francis, 83, had a sharp encounter with a woman on Tuesday evening during a walkabout in St. Peters Square.