Footage of the incident was uploaded to social media.
A teacher was stabbed to death at a school in northern France by a radicalised former pupil in what Emmanuel Macron, the French President, called a case of barbaric “Islamist terrorism”.
Gérald Darmanin, France’s interior minister, said there was a link between the attack and the war in Israel.
Dominique Bernard, a French literature teacher, was killed trying to “protect” pupils at City School Gambetta-Carnot in Arras and in doing so “saved many lives”, said Mr Macron.
He added that another attack at a school elsewhere in France had been foiled.
A security guard and sports teacher were also seriously injured in the attack, in which the assailant reportedly shouted “Allahu Akbar” - God is great in Arabic. No pupils were hurt.
The suspect, 20, identified as Mohammed Mogouchkov, is reportedly of Russian nationality and had been under “active” surveillance, including by being “bugged” and trailed by the DGSI, France’s domestic intelligence service.
Checks were carried out on the suspect the day before the murder and he had been placed on a terror watch list just 11 days before the attack, according to reports.
However, agents found no evidence he was about to act.
A former member of staff at the school said the suspect had been suspended when he was a pupil for attacking a teacher, and that colleagues were “afraid to turn their backs on him”.
The murder came almost three years to the day after Samuel Paty, another secondary school teacher, was killed and beheaded in a Paris suburb by an 18-year-old Islamic terrorist of Chechen origin.
Mr Paty was slain on Oct 16 2020, after a student alleged he had shown his pupils Charlie Hebdo’s 2012 cartoons depicting the Islamic prophet Muhammed during a class on freedom of expression.
Prosecutors have launched an anti-terror investigation into Friday’s killing.
While no motive was given, Macron said: “Once again a school has been struck by the barbarity of Islamist terrorism”.
The attack also comes with tensions rising in France, which has Europe’s largest Jewish and Muslim communities, after Saturday’s attack by Hamas on Israel.
Macron stopped short of making a direct link but said: “Terrorism strikes once again in a school, and in a context that we all know.”
Calling on the French to remain “united”, he said the school would reopen on Saturday as “our choice is made not to give in to terror, not to let anything divide us”.
France has been targeted by a series of Islamist attacks over the years, the worst being a simultaneous assault by gunmen and suicide bombers on entertainment venues and cafes in Paris in November 2015.
Police were called to the school in Arras shortly after 11am on Friday morning.
His older brother Mosvar is serving a five-year prison term over a plot to “target the Elysée” in a Kalashnikov attack, according to Le Parisien.
The plot was foiled after a French secret agent infiltrated the gang, according to the newspaper.
Without residency papers, the entire family was due to be expelled from France in 2014. But, at the last minute, they were allowed to stay after anti-racism charities intervened.