France was on high alert on Saturday, after an attacker stabbed a teacher to death in what the president called an act of "Islamist terror," with troops deployed and major attractions including the Louvre museum and Palace of Versailles evacuating visitors.

Friday's attack took place in the northeastern town of Arras, home to large Jewish and Muslim populations.

A man in his twenties killed French teacher Dominique Bernard and severely wounded three others at the school he used to attend.

On Saturday, amid fears the conflict between Israel and Hamas could lead to violence in foreign capitals, France announced it would deploy up to 7,000 soldiers under the highest warning level.

Police arrested the suspected perpetrator of Friday's attack, Mohammed Moguchkov, who had cried the Arabic phrase "Allahu akbar!" (God is greatest).

He was among 11 people being held in custody on Saturday, a police source told AFP, including his 17-year-old brother and several other family members.

In Paris, the famous Louvre museum evacuated visitors and closed following a "security" threat.

A spokeswoman for the Louvre, the largest museum in the world, told AFP it had "received a written message stating that there was a risk to the museum and its visitors".

The Palace of Versailles, also a major tourist attraction just outside the capital, was evacuated due to a bomb threat made anonymously online, police sources told AFP.

The deployment of the soldiers from Operation Sentinelle will be completed by Monday evening, according to the Elysee presidential palace.

Sentinelle is a French military operation involving the deployment of soldiers, police and gendarmes set up in the aftermath of January 2015 attacks to protect parts of the country deemed sensitive from terrorism.

"This school was struck by the barbarity of Islamist terrorism," President Emmanuel Macron said after visiting the school, adding the victim had "probably saved many lives" with his courage in blocking the attacker.

Macron said another attempted attack outside Paris had been foiled by security forces.

According to the interior ministry, the president was referring to the arrest of a "radicalised" man arrested leaving a prayer hall in the Yvelines region bordering Paris for carrying a prohibited weapon.

Interior Minister Gerald Darmanin later said there was "probably a link between what's happening in the Middle East and this incident" in Arras.

France upped its alert level to maximum following a crunch security meeting Friday, the prime minister's office told AFP.

The national anti-terrorist prosecutor announced it has opened an investigation.

French authorities said Moguchkov was Russian, born in the predominantly Muslim North Caucasus republic of Ingushetia.

He was already on a French national register as a potential security threat, a police source told AFP, and under electronic and physical surveillance by France's domestic intelligence agency, the DGSI.

Bernard was stabbed in the throat and chest. Among those wounded were a school security guard who was stabbed multiple times and is fighting for his life, and a teacher in a less serious condition.

A cleaner was also hurt, according to anti-terror prosecutor Jean-Francois Ricard.

No pupils at the school were hurt. (AFP)