Three people have been killed in a knife attack in the French city of Nice, police say.
Nice Mayor Christian Estrosi said everything pointed to a “terrorist attack at the heart of the Notre-Dame basilica”.
Police said one woman had her throat cut in the attack and Mr Estrosi spoke of “islamofascism”. The suspect was detained shortly after the attack.
France’s national anti-terror prosecutors opened a murder inquiry.
The mayor told reporters that the suspect had “repeated endlessly ‘Allahu Akbar’ (God is greatest) when he was being treated at the scene”.
Mr Estrosi said one of those killed was the caretaker at the basilica. It later emerged that worshippers were inside the building at the time of the attack and that a witness had managed to raise the alarm with a special protection system set up by the city.
The 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.
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.