About 4000 soldiers – potentially rising to 7000 – were deployed to protect sites including places of worship and schools in France and was at its highest level of security alert after the second deadly knife attack in its cities in two weeks.
Police were holding a 21-year-old Tunisian migrant, Brahim al-Aouissaoui, over the attack in which a man shouting “Allahu Akbar” (God is Greatest) decapitated a woman and killed two other people in Notre Dame Basilica in Nice on Thursday.
The attack took place at a time of growing anger among Muslims in many countries over the issue of French cartoons of the Prophet Mohammad, which they deem insulting and blasphemous.
It occurred almost two weeks after Samuel Paty, a school teacher in a Paris suburb, was beheaded by an 18-year-old Chechen. Paty had shown his pupils such cartoons in a class on freedom of expression.
France, home to Europe’s largest Muslim community and hit by a string of militant attacks in recent years, has defended the right to publish such cartoons. Macron has insisted France will not compromise on its basic freedoms of belief and expression.
People gathered in front of the Notre Dame church to lay flowers and light candles.
French embassies were also told to step up security.
Meanwhile in nations such as Pakistan, Bangladesh, Palestine, India, Lebanon and Somalia hundreds of Muslims staged anti-French protests.