French president Emmanuel Macron vowed his country would stand firm against religious extremists after a knife-wielding man killed three people at a church, in the country's second attack blamed on Islamist terrorism this month.

France will not "give up on our values," Macron said in Nice, after a Tunisian migrant went on a near half-hour rampage with a 30-centimetre (12-inch) knife, targeting people praying in the southern city's Notre-Dame basilica.

People lights candle outside the Notre-Dame de l'Assomption Basilica in Nice in tribute to the three victims of a knife rampage, which France's president called an 'Islamist terrorist attack' People lights candle outside the Notre-Dame de l'Assomption Basilica in Nice in tribute to the three victims of a knife rampage, which France's president called an 'Islamist terrorist attack' Photo: AFP / Valery HACHE

A 60-year-old woman died inside the church and the body of a man, a 55-year-old church employee, was found nearby, his throat also slit.

Another woman, a 44-year-old Brazilian who had fled the church to a nearby restaurant, died shortly afterwards from multiple knife wounds.

"Tell my children I love them," she managed to say before her death, according to French cable channel BFM TV.

The church killings come after the October 16 beheading of a history teacher Samuel Paty by an extremist in a Paris suburb after he showed pupils cartoons of the Prophet Mohammed in a free speech lesson The church killings come after the October 16 beheading of a history teacher Samuel Paty by an extremist in a Paris suburb after he showed pupils cartoons of the Prophet Mohammed in a free speech lesson Photo: AFP / Valery HACHE

The assailant, who was shot and wounded by police, was identified as 21-year-old Brahim Aouissaoui, who arrived in Italy last month, then travelled to France, judicial sources said.

Aouissaoui who had a copy of the Koran and three knives with him, shouted "Allahu Akbar" (God is Greatest) when approached by police who shot and seriously wounded him, France's anti-terror prosecutor Jean-Francois Ricard told a press conference.

Nice Mayor Christian Estrosi told journalists at the scene the attacker "kept repeating 'Allahu Akbar' even while under medication" as he was taken to hospital.

The assailant, who was shot and wounded by police, was identified as 21 year-old Brahim Aouissaoui, who arrived in Italy last month, then travelled to France, judicial sources said The assailant, who was shot and wounded by police, was identified as 21 year-old Brahim Aouissaoui, who arrived in Italy last month, then travelled to France, judicial sources said Photo: POOL / ERIC GAILLARD

The church killings come after the October 16 beheading in a Paris suburb of history teacher Samuel Paty by an extremist after Paty showed pupils cartoons of the Prophet Mohammed in a free speech lesson.

Macron defended the cartoons and the right to mock religion, sparking widespread anger against France in the Islamic world and several campaigns in Muslim-majority countries to boycott French products.

Daniel Conilh, a 32-year-old waiter at Nice's Grand Cafe de Lyon, a block from the church, said it was shortly before 9:00 am when "shots were fired and everybody took off running".

Map of France showing recent knife attacks. Map of France showing recent knife attacks. Photo: AFP / Robin BJALON

"A woman came in straight from the church and said, 'Run, run, someone has been stabbing people'," he told AFP.

French anti-terror prosecutors are handling the inquiry into charges related to a "terrorist murder".

The police who shot Aouissaoui had "without any doubt prevented an even higher toll," said chief prosecutor Jean-Francois Ricard, adding investigators had found two unused knives in a bag at the scene.

IMAGES French President Emmanuel Macron arrives at the Notre-Dame de Nice basilica after the knife attack that killed three people. IMAGES French President Emmanuel Macron arrives at the Notre-Dame de Nice basilica after the knife attack that killed three people. Photo: AFPTV / Fabien NOVIAL

The killings, which occurred ahead of the Catholic holy day of All Saints Day on Sunday, prompted the government to raise the terror alert level to the maximum "emergency" level nationwide.

France has been on high alert since the January 2015 massacre at the satirical weekly magazine Charlie Hebdo marked the beginning of a wave of jihadist attacks that have killed more than 250 people.

Tensions have heightened since last month, when the trial opened for 14 suspected accomplices in that attack.

The paper marked the start of the court proceedings by republishing cartoons of the Prophet Mohammed that infuriated millions of Muslims worldwide -- the same caricatures that teacher Samuel Paty used as lesson material.

Days after the trial opened, an 18-year-old man from Pakistan seriously injured two people with a meat cleaver outside Charlie Hebdo's former offices in Paris.

In Nice, Macron announced increased surveillance of churches by France's Sentinelle military patrols, to be bolstered to 7,000 troops from 3,000.

Security at schools would also be boosted, he said.

But some claim Macron is unfairly targeting France's estimated five to six million Muslims -- the largest community in Europe.

Macron on Thursday urged people of all religions to unite and not "give in to the spirit of division".

After Thursday's attack, Malaysia's former prime minister Mahathir Mohamad tweeted that "Muslims have a right to be angry and to kill millions of French people for the massacres of the past".

Twitter later deleted his post.

Thursday also saw a Saudi citizen wound a guard in a knife attack at the French consulate in Jeddah while police in the French city of Lyon said they had arrested an Afghan spotted carrying a knife while trying to board a tram.

In Nice, painful memories remain fresh of a jihadist attack during Bastille Day celebrations on July 14, 2016, when a man rammed his truck into a crowded promenade, killing 86 people.