Three people have been killed in a knife attack in the French city of Nice, police say.
Nice Mayor Christian Estrosi said there had been a "terrorist attack at the heart of the Notre-Dame basilica".
One elderly victim who had come to pray was "virtually beheaded". A suspect was shot and detained shortly afterwards.
Mr Estrosi spoke of "Islamo-fascism" and that the suspect had "repeated endlessly 'Allahu Akbar' (God is greatest)."
France's national anti-terror prosecutors have opened a murder inquiry. Mr Estrosi compared the attack to the recent murder of teacher Samuel Paty, who was beheaded close to his school outside Paris earlier this month.
Two further attacks took place on Thursday morning, one in France and one in Saudi Arabia.
A man was shot dead in Montfavet near Avignon after threatening police with a handgun. And a guard was attacked outside the French consulate in Jeddah. A suspect was arrested and the guard taken to hospital.
Police have not suggested a motive for the attack. However, it follows days of protests in some Muslim-majority countries triggered by President Macron's defence of French cartoons that depict the Prophet Mohammed. There have been calls in some countries for a boycott of French goods.
What is known about the attack in Nice?
Two of those who died were attacked inside the church, the elderly woman and a man who was found with his throat cut, reports said.
A woman managed to flee to a nearby cafe after being stabbed several times, but died later.
It later emerged that a witness had managed to raise the alarm with a special protection system set up by the city.
Chloe, a witness who lives near the church, told the BBC: "We heard many people shouting in the street. We saw from the window that there were many, many policemen coming, and gunshots, many gunshots."
Tom Vannier, a journalism student who arrived at the scene just after the attack, told the BBC that people were crying on the street.
French police officers stand at the entrance of the Notre Dame Basilica church in Nice, France, 29 October 2020
France's interior minister appealed to people to avoid the area in the centre of the French Riviera city. Gérald Darmanin said he was convening a crisis meeting at the ministry in Paris. President Emmanuel Macron will visit the scene later on Thursday.
A minute's silence was held in the National Assembly, where Prime Minister Jean Castex had just been giving details of Covid-19 lockdown measures coming into force on Thursday night.
"Without question this is a very serious new challenge that is striking our country," he said, appealing for unity and cohesion.
The French Council of the Muslim Faith condemned the Nice knife attack and spoke of its solidarity with the victims and their families.
What's the context?
Nice was the target of one of France's deadliest attacks in recent years, when a 31-year-old Tunisian drove a truck into crowds celebrating Bastille Day on 14 July 2016, killing 86 people.
Days later a priest, Father Jacques Hamel, had his throat cut during morning Mass at a church in Rouen.
Thursday's attack has echoes of another attack earlier this month near a school north-west of Paris. Samuel Paty, who was a teacher in Conflans-Sainte-Honorine, was beheaded days after showing controversial cartoons of the Prophet Muhammad to some of his pupils.
The murder has heightened tensions in France and the government's attempt to crack down on radical Islam has angered Turkey and other countries.
Turkish President Recep Tayyip Erdogan has called for a boycott of French goods.
The situation worsened after a cartoon on Mr Erdogan appeared in the satirical magazine Charlie Hebdo.
https://www.bbc.com/news/world-europe-54729957
