By Pascal Rossignol, Layli Foroudi and Michel Rose

ARRAS, France A 20-year-old man fatally stabbed a teacher and gravely wounded two other people in an attack at a school in the northern France city of Arras on Friday that President Emmanuel Macron condemned as "barbaric Islamic terrorism."

Interior Minister Gerald Darmanin said France was now on its highest state of alert and that the Arras attack bore a link to events in the Middle East, where Israel is conducting a military offensive to root out Hamas fighters after their deadly rampage.

Only a day earlier, Macron had urged the French to remain united and refrain from bringing the Israel-Hamas conflict home.

Visiting the site of the attack, Macron paid his respects to the dead teacher, Dominique Bernard, whose body still lay under a cover surrounded by a pool of blood.

"(He) stepped in and undoubtedly saved a lot of lives himself," Macron said. "Our choice is made not to give in to terror, not to let anything divide us."

The suspect, identified by prosecutors as Mohamed M., who has been arrested, was a former student of the Lycee Gambetta high school where the attack happened, a police source said. One of the attackers' brothers was also detained nearby.

The investigation was handed to the anti-terrorism prosecutor's office.

Numerous witnesses heard Friday's attacker shouting "Allahu Akbar", according to prosecutor Jean-Francois Ricard.

The attacker was on a state watchlist of people known as a potential security risk, a police source said. The "Fiche S" contains thousands of names and only a small number are actively monitored.

Darmanin said the man had been monitored by intelligence services, with his phone having been tapped for the past few days because authorities had noticed suspicious behaviour but no indication of a planned attack.

The man was described by the police source as a Russian-born Chechen but by some French media as a Russian-born Ingush.

A security source said an elder brother of the alleged assailant was serving time in prison for links to Islamist militant networks and glorification of terrorist acts.

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.

INCREASED SECURITY

Darmanin said the state of alert had not been raised in response to a particular threat.

In 2020, a teacher, Samuel Paty, was beheaded by a Chechen teenager who wanted to avenge his use of cartoons mocking the Prophet Mohammad during a class on freedom of expression.

"Once again a school was hit by the barbarity of Islamic terrorism," Macron said.

A video obtained by Reuters showed three people - one of them with a chair - trying to stop the attacker in the school's parking lot and getting struck by him. "He's got a knife, he's got a knife," one of those watching the scene said.

Philosophy teacher Martin Doussau said he was chased down by the attacker but managed to escape unharmed after locking himself in a room. The assailant did not appear to be wanting to settle a grudge, he added

"He was looking for a history teacher," Doussau told Reuters. "That's what leaves me thinking this wasn't ... about settling a personal vendetta with a teacher."

A security alert was triggered later at another school in Arras, a school worker told Reuters. A third man was arrested in that incident, when he tried to enter the school with a suspicious backpack, French media reported.

Education Minister Gabriel Attal said security would be reinforced in schools throughout France.

Macron said another attack had been prevented on Friday in the wider Paris region.

Pupils were confined to their classrooms for hours.

Louis, a 15-year-old pupil, said students initially assumed it was a drill, when the alarm rung and they had to hide.

"It shows it can happen anywhere," he told Reuters.

Arras is a city in the de-industrialised, ethnically diverse northern corner of France, a region where the far right enjoys strong support.

(Reporting by Pascal Rossignol and Ardee Napolitano in Arras and Michel Rose, Layli Foroudi, Charlotte Van Campenhout, Tassilo Hummel, Benoit van Overstraeten, Blandine Henault in Paris; Writing by Ingrid Melander; editing by Richard Lough, Deborah Kyvrikosaios and Jonathan Oatis)