It was the third attack in two months in France that authorities have attributed to Muslim extremists, including the beheading of a teacher. It comes during a growing furor over caricatures of the Prophet Muhammad that were republished by the satirical newspaper Charlie Hebdo — renewing vociferous debate in France and the Muslim world over the depictions that Muslims consider offensive but are protected by French free speech laws.

Other confrontations and attacks were reported yesterday in the southern French city of Avignon and in the Saudi city of Jiddah, but it was not immediately clear if they were linked to the attack in Nice.

French President Emmanuel Macron said he would immediately increase the number of soldiers deployed to protect schools and religious sites from around 3,000 currently to 7,000. French churches have been ferociously attacked by extremists in recent years, and yesterday's killings come ahead of the Roman Catholic All Saints' holiday.

“He cried ‘Allah Akbar!’ over and over, even after he was injured,” said Nice Mayor Christian Estrosi, who said a woman and a man died inside the church, while a second woman fled to a nearby bar but was mortally wounded. “The meaning of his gesture left no doubt.”