Police officers stand guard outside the high school where a man stabbed a teacher in Arras, France, on Saturday. AP

French President Emmanuel Macron has ordered 7,000 soldiers to be mobilised for increased security patrols, his office said on Saturday, a day after a teacher was stabbed to death in an attack.

The attack on Friday was denounced by Macron as an act of "terror" in Arras, which has large Jewish and Muslim populations.

France was put on its highest security alert on Friday after a 20-year-old man fatally stabbed a teacher and gravely wounded two other people in an attack at a school in the city of Arras in northern France.

Macron's office said that the soldiers would be mobilised by Monday evening until further notice as part of an ongoing operation that regularly conducts patrols in major city centres and tourist sites.

The security alert comes as France hosts the Rugby World Cup and prepares to face South Africa on Saturday evening in their quarter-final.

France's anti-terror 'Vigipirate' officer stands at the fort of Vincennes on the outskirts of Paris. File/AFP

France has been targeted by a series of 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.

Interior Minister Gerald Darmanin said on Friday 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 into Israel last Saturday.

Reuters