Pope Francis has defended the right to freedom of expression but has said it was wrong to provoke others by insulting their religion.

His comments followed the fatal attack on the satirical magazine Charlie Hebdo in Paris last week.

To illustrate his point, the pontiff told journalists on the papal plane his assistant could expect a punch if he ''cursed his mother''.

''It's normal - you cannot provoke, you cannot insult the faith of others,'' he said.