French President Emmanuel Macron said on Saturday he respected Muslims who were shocked by cartoons of the Prophet Mohammad but that was no excuse for violence, as his officials ramped up security after a knife attack in a French church that killed three people this week.

An assailant shouting "Allahu Akbar" (God is greatest) beheaded a woman and killed two other people in a church in Nice on Thursday, in France's second deadly knife attack in two weeks with a suspected Islamist motive...