Three people were killed and several others wounded in a stabbing attack in Nice, French media reported.
The mayor of Nice, Christian Estrozzi, said that one person had been arrested.
“Everything points to a terrorist attack in the heart of Notre Dame,” he added.
The interior minister appealed to citizens to avoid the area in the middle of the French Riviera.
According to French reports, a man and a woman were killed in the attack and the suspect was arrested 10 minutes later, before being taken to hospital.
Police said the woman had been slaughtered, and the city’s mayor spoke of what he described as “Islamic fascism.”
The mayor told reporters that the suspect “kept repeating the phrase (God is Great) when the police were dealing with him at the scene of the accident.”
Estrozzi added that one of the dead was the pastor of the church.
It later emerged that the worshipers were inside the building at the time of the attack and that one of the witnesses was able to sound the alarm using a special protection system set up by the city’s municipality.
The French Islamic Council condemned the attack and expressed its solidarity with the victims and their families.
The Public Prosecutor for Combating Terrorism in France opened an investigation into the incident.
A minute of silence was observed in the National Assembly, as Prime Minister Jean Castex was giving details of the closure measures that would take effect on Thursday evening.
“There is no doubt that our country faces a serious challenge,” he said, calling for unity and cohesion.
aTo terror Hits again
The city of Nice was the target of one of the bloodiest attacks in France in recent years, when a 31-year-old Tunisian drove a truck that ran over crowds celebrating Bastille Day on July 14, 2016, killing 86 people.
Days later, the priest, Jack Hamel, was murdered during morning mass in a church in Rouen.
Earlier this month, teacher Samuel Batey was beheaded near a school northwest of Paris, days after he showed some of his students’ controversial cartoons of the Prophet Muhammad.