French President Emmanuel Macron has decried the terrorist attack on a church in Nice this morning in which three people died.
An elderly parishioner who had come to pray at the basilica of Notre-Dame was "virtually beheaded" in the knife attack, the BBC reports.
President Macron has arrived in Nice to visit the scene of what he called an "Islamist terrorist attack".
Speaking to reporters, he said protection would be stepped up at schools and places of worship, including churches.
"I would like to express the support of France towards the Catholic community," he said.
He continued: "France is under attack ... If we are attacked it is because of our values of freedom and our desire not to yield to terror."
Christian Estrosi, mayor of the southern French city, said the attacker had "repeated endlessly 'Allahu Akbar'" (God is greatest).
He drew comparisons with the murder of teacher Samuel Paty, who was beheaded near his school in a suburb of Paris earlier this month after showing students cartoons of the Prophet Muhammad.
He said a suspect has been arrested in connection with the Nice attack.
Guinean Cardinal Robert Sarah said Islamist terorism posed a threat to the whole of the West.
"Islamism is a monstrous fanaticism which must be fought with force and determination," he wrote on Twitter.
He added: "The West, today France, must understand this. Let us pray."
Nice was the scene of another terror attack in 2016 when a lorry was driven into crowds of people celebrating Bastille Day. The Islamic State claimed responsibility for the attack, which killed 86 people.