Iran Press/ Europe: 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 after the attack.
The attack comes while France is still reeling from the beheading earlier this month of French middle school teacher Samuel Paty by a Chechen origin man.
It was not immediately clear what the motive was for the Nice attack.
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