Jihadis expanded their hate crimes with the killing of three more French nationals, including a woman, while a guard at the French embassy in Saudi Arabia was attacked with a knife by a Saudi national.
A man shouting 'Allahu Akbar' beheaded a woman and killed two others outside a church in the southern French city of Nice.
The slaying that comes within days after a French middle school teacher, Samuel Paty, was beheaded by another Muslim fundamentalist of Chechen origin.
Officials said a man wielding a knife slit the throat of one person and killed two others. Several other people were also injured in the attack.
One elderly victim who had come to pray was "virtually beheaded". A suspect was shot and detained shortly afterwards.
Reuters quoted a police source as saying that a woman was feared to have been decapitated in the knife attack. The attacker was swiftly detained following the incident in the morning. French anti-terror prosecutors have opened an inquiry into the incident.
"The situation is now under control," police spokeswoman Florence Gavello said.
French interior minister Gerald Darmanin convened a crisis meeting after the attack.
The Mayor of Nice described the attack as an act of “terrorism”. According to Mayor Christian Estrosi, the attack took place in or near the city's Notre Dame church and one of those killed was the caretaker at the basilica.
A police source was reported as saying that while two victims died at the Basilica of Notre Dame, a third succumbed to injuries after seeking refuge in a nearby bar.
The Mayor told reporters that the suspect had "repeated endlessly 'Allahu Akbar' (God is greatest) when he was being treated at the scene" after being injured during his arrest.
Estrosi spoke of "Islamo-fascism" and said the suspect had "repeated endlessly 'Allahu Akbar' (God is greatest)".
Estrosi said President Emmanuel Macron would soon be arriving in Nice and demanded additional security for churches around the country.
Fundamentalist Islamic nations led by Turkey have ganged up against French President Emmanuel Macron’s comments in Prophet’s cartoon row, rather than condemning the beheading of the school teacher.
Turkish President Recep Tayyip Erdogan has called on islamic nations to boycott France while fundamentalists in Bangladesh capital Dhaka rallied in protest against Macron.
India condemned the slaying of the French teacher and called attacks on Macron as 'violation of international discourse.'
While the attacker had killed Paty as a ‘punishment’ for showing school children cartoons of Prophet Mohammad during a class lesson, the motive behind the Nice attack was not immediately clear.
But it follows protests in some Muslim-majority countries triggered by President Macron's defence of the publication of cartoons that depicted the Prophet Mohammed.
French officials have supported the right to display the cartoons and Macron has said he will fight extremism to the end.