One of three people stabbed to death in Nice has been named as church worker Vincent Loques.
Local politician Eric Ciotti tweeted a picture of Mr Loques dressed in a t-shirt, looking relaxed and smiling.
He said Mr Loques was a "devoted employee" of the Notre Dame church, where the attack took place.
One of the other victims - a woman - was decapitated.
She and Mr Loques are said to have died at the scene, while another woman made it out of the church and died at a local cafe.
Mr Loques was 55 and a father of two, La Parisien newspaper reported.
Members of the parish said he had been church warden for ten years and was "expansive and sympathetic".
The attacker - who was shot by police and taken to hospital - is reportedly a 21-year-old Tunisian national.
He is thought to have entered France recently from neighbouring Italy, a police source told the Reuters news agency.
He is believed to have been acting alone, two police officials told the AP news agency.
Nevertheless, Prime Minister Jean Castex has told residents of Nice only to leave the house for food shopping, commuting to work, medical reasons or pressing family matters.
Nice's mayor, Christian Estrosi, tweeted that the attacker shouted "Allahu Akbar [God is greatest]" several times.
"Everything suggests a terrorist attack," he added.
France's anti-terrorism prosecutor has opened an investigation, as has the anti-terrorism court prosecutor in Tunisia.
President Emmanuel Macron, who visited Nice on Thursday afternoon, said his country had been "attacked" and expressed the "support of France towards the Catholic community".
He added that the number of soldiers deployed to protect schools and religious sites would be increased from about 3,000 at the moment to 7,000.
Reuters journalists at the scene said police armed with automatic weapons put up a security cordon around the church, which is on Nice's Jean Medecin avenue, the city's main shopping thoroughfare.
Sounds of explosions could be heard as sappers detonated suspicious objects.
A representative of the French Council for the Muslim Faith condemned the attack, saying. "As a sign of mourning and solidarity with the victims and their loved ones, I call on all Muslims in France to cancel all the celebrations of the holiday of Mawlid (Prophet Muhammad's birthday)."
In a separate incident shortly after, French police confirmed a man was shot dead near Avignon, after threatening passers-by with a handgun in the district of Montfavet.
In Jeddah, Saudi Arabia, a man was arrested after stabbing and wounding a guard at the French consulate, state media reported.
It comes as the country remains under high alert for terrorist attacks following the beheading earlier this month of French middle school teacher Samuel Paty in Paris.
The attacker had said he wanted to punish Mr Paty for showing pupils cartoons of the Prophet Mohammad in a civics lesson.
Mr Estrosi said the victims in Nice had been killed in a "horrible way".
"The methods match, without doubt, those used against the brave teacher in Conflans Sainte Honorine, Samuel Paty."
He added: "Attack in Nice, attack in Avignon, attack on the French consulate in Saudi Arabia. It is not a coincidence."
Since Mr 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.
That has prompted an outpouring of anger in parts of the Muslim world, with some governments accusing President Macron of pursuing an anti-Islam agenda.
