The knifeman shouted “Allahu Akbar” during the attack at a school in Arras, northern France. Currently, he is in custody.

Previous counter-terror cases have used the “attack emergency” level.

Extra security deployments and public warnings can be triggered by the alert.

The Louvre Museum in Paris was closed for security reasons on Saturday due to the mobilization of 7,000 soldiers.

The Palace of Versailles was evacuated on Saturday following a bomb threat, police told French news agency AFP.

According to AFP, the alert came via anonymous message on the internet, adding that the palace would be closed for the rest of the day.

Due to the conflict between Israel and Hamas, tensions among France’s large Muslim and Jewish communities have been rising since Friday’s attack at Gambetta high school in the northern city.

According to Darmanin, there is “no doubt” that the Arras attack was linked to the Israel-Hamas conflict.

Mohamed Mogouchkov, 20, is of Chechen descent and known to security services for his involvement with Islamist extremism, according to the police.

Reports say he alarmed teachers with his extremist language while a pupil at the school.

Several members of the assailant’s family were also arrested – a 17-year-old brother, his mother, a sister, and an uncle.

After a security meeting with President Emmanuel Macron, Prime Minister Elisabeth Borne took the urgent step.