Prime Minister Gabriel Attal said in a post on X that the decision, which comes months before Paris hosts the Olympic Games, was taken "in light of the Islamic State's claiming responsibility for the (Moscow) attack and the threats weighing on our country".
The announcement came after President Emmanuel Macron held an emergency security meeting prompted by Friday’s attack in a Moscow suburb that killed at least 137 people, according to Russian investigators.
The IS group's Afghan affiliate has claimed responsibility for the massacre, Europe's deadliest terrorist attack claimed by the jihadist group.
France's terror alert system has three levels, and the highest level is activated in the wake of an attack in France or abroad or when a threat of one is considered to be imminent.
It allows for exceptional security measures such as stepped-up patrols by armed forces in public places like train stations, airports and religious sites.
France has repeatedly been hit by deadly jihadist attacks, including the Bataclan concert hall massacre in 2015 in which extremists opened fire on concert-goers and held hostages for hours.
The country was already on high security alert ahead of the Paris Olympics and Paralympics this year, which are expected to draw millions of visitors to the country.
Security concerns are notably high for the the exceptional opening ceremony on July 26, which will involve boats riding along the Seine River and huge crowds watching from the embankments.
France24
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