France raised its security alert to the highest level after a knife-wielding attacker stabbed a teacher to death outside a school in the northeastern French town of Arras on Friday.

According to police, the teacher was killed in front of the main entrance to the school. He was stabbed in the throat and chest before the assailant entered the building and continued his attack, police said.

The raised alert level allows for larger police and military deployments to protect the country.

Police said two more people, another teacher and a technical assistant, were seriously injured in Friday's attack, but none of the pupils were said to have been hurt.

The assailant, who police say shouted "Allahu Akbar" (God is great) during the attack, has been arrested and France's national anti-terror prosecution office has opened an investigation, pointing to a suspected terror motive for the attack. 

What do we know about the assailant?

The attacker has been named as Mohammed Mogouchkov, a 20-year-old Russian national from the southern Caucasus region of Chechnya, police sources said.

The same sources said Mogouchkov first arrived in France in 2008, and was already known to French security services (DGSI) for suspected radicalization.

Indeed, Mogouchkov, a former student at the school, according to French broadcasters France Info and BFM, had been stopped and searched by police on Thursday this week, a source told the French AFP news agency.

Mogouchkov's brother has also been taken into custody, according to French broadsheet Le Figaro, citing Interior Ministry sources. 

What did Macron say?

French President Emmanuel Macron condemned the "barbarity of Islamic terrorism."

Speaking from the courtyard of the Gambetta high school where the attack took place, Macron called on the French people to "remain united, pull together and stand up."

He added: "The choice has been made to not give in to terror, to not let anything divide us."

He also said "the teacher that was killed probably helped save many lives" and revealed that police had foiled another attempted attack in another part of France.

A vice president of the lower house of parliament, Naima Moutchou, said the National Assembly "expresses its solidarity and thoughts for the victims, their families, and the educational community as we learn that a teacher has been killed and several others have been injured.''

What's the bigger picture?

The attack comes almost three years to the day after the beheading of teacher Samuel Paty in broad daylight in 2020 near his school in a Paris suburb by a radicalized Chechen refugee.

"Three years after the assasination of Samuel Paty, terrorism has struck a school again and in a context that we all know," Macron said.

The attack also came with French security services on high alert given the escalating conflict in the Middle East, and given that France has large Jewish and Muslim populations.

rc,mf/sms (AFP, AP, dpa, Reuters)