A lorry has struck a crowd after Bastille Day celebrations in the southern French city of Nice, killing at least 80 people and injuring dozens, officials say.
It happened on the famous Promenade des Anglais after a firework display. The driver was shot dead and guns and grenades were found inside the lorry.
President Francois Hollande said the attack was of a "terrorist nature".
He has extended a state of emergency by three months.
France had been on high alert following last November's attacks in Paris in which 130 people died and hundreds were wounded.
The state of emergency had been due to end on 26 July.