An attacker with a knife killed three people, including a woman who was decapitated, at a church in the French city of Nice on Thursday, police said, in an incident the city's mayor described as terrorism.
Mayor Christian Estrosi said on Twitter the knife attack had happened in or near the city's Notre Dame church and that police had detained the attacker.
Police said two people were confirmed to have died in the attack and several were injured.
A police source said a woman was decapitated. French politician Marine Le Pen also spoke of a decapitation having occurred in the attack.
The attack comes while France is still reeling from the beheading earlier this month of French middle school teacher Samuel Paty in Paris by a man of Chechen origin.
The attacker had said he wanted to punish Paty for showing pupils cartoons of the Prophet Mohammad in a civics lesson.
It was not immediately clear what the motive was for the Nice attack, or if there was any connection to the cartoons, which Muslims consider to be blasphemous.
Since Paty's killing, French officials - backed by many ordinary citizens - have re-asserted the right to display the cartoons, and the images have been widely displayed at marches in solidarity with the killed teacher.
hat has prompted an outpouring of anger in parts of the Muslim world, with some governments accusing French leader Emmanuel Macron of pursuing an anti-Islam agenda.