European Union leaders expressed solidarity with France on Thursday and pledged to confront "those that seek to incite and spread hatred" after a knifeman killed three in a Nice church.
"I condemn the odious and brutal attack that has just taken place in Nice and I am with France with all my heart," European Commission president Ursula von der Leyen tweeted.
"My thoughts are with the victims of this hateful act. All of Europe is in solidarity with France. We will remain united and determined in the face of barbarity and fanaticism."
Charles Michel, the president of the European Council, dubbed the attack "abominable" and declared: All of Europe is with you."
And David Sassoli, speaker of the European Parliament, said: "We have a duty to stand together against violence and those that seek to incite and spread hatred."
French anti-terror prosecutors have opened an inquiry into the attack, in which a man wielding a knife entered the Basilica of Notre-Dame in the Mediterranean city of Nice and killed three people.
France was already on a heightened state of tension in the wake of the October 16 murder of a history teacher, Samuel Paty, who had been denounced by Muslim parents after showing pupils cartoons of the Prophet Mohammed.
After the killing, French President Emmanuel Macron defended the right of cartoonists to lampoon religious figures, and anti-French protests have erupted in parts of the Muslim world.