The level was upped after a security meeting attended by President Emmanuel Macron on Friday evening, the office said.

Earlier on Friday a man of Chechen origin stabbed to death a teacher and severely wounded two other adults in the town of Arras.

LATEST: What we know so far about the French school terror attack

Speaking at a press conference on Friday evening, interior minister Gérald Darmanin said the attack was “undoubtedly linked” to the situation in Israel and Palestine.

Earlier, Macron has said that security services foiled a second attack on Friday, believed to be in the greater Paris region.

Darmanin added that eight people are now in custody in relation to the Arras attack, including the attacker and his brother – both of whom had previously been placed on a terror watchlist for extremism.

The attacker had been under “active surveillance” by French security services since late July. 

“This school was struck by the barbarity of Islamist terrorism,” Macron said after visiting the school in Arras, saying the victim had “probably saved many lives” with his courage in seeking to block the attacker.

The suspected attacker, Mohammed Moguchkov, who is in his 20s, is from Russia’s mainly Muslim southern Caucasus region of Chechnya, but had lived in France since he was a child.

Moguchkov cried the Arabic phrase “Allahu akbar!” (God is greatest!), according to the preliminary elements of the investigation.

The victim, a French teacher named by media as 57-year-old Dominique Bernard, was stabbed in the throat and chest.

Those wounded were a member of non-teaching staff who was stabbed multiple times and is fighting for his life and a sports teacher who is in a less serious condition.