France fears it could be a target for terrorists looking to replicate Friday's concert hall attack in Moscow that killed at least 137 people.

Prime Minister Gabriel Attal wrote on X that the country has raised its terror alert — known as the Vigipirate system — to its highest level as a result.

With the nation set to host the Olympic Games in Paris this summer, Attal said the government made the decision after a meeting on Sunday of the National Defense and Security Council that was chaired by President Emmanuel Macron.

Attal said the change was necessary "in light of the Islamic State's claiming responsibility for the (Moscow) attack and the threats weighing on our country".

The state-owned international news channel France 24 said the threats included emails sent to students that said there would be attacks at high schools in the country's north.

Macron said on Monday that France had information that "an entity of Islamic State… planned the (Moscow) attack and carried it out", AFP reported. He added "this particular group made several attempts (at attacks) on our own soil".

Reuters said Attal's office explained: "The claim for the Moscow attack comes from the Islamic State in Khorasan. This organization is threatening France and has been involved in a number of recent foiled attacks in several European countries, including Germany and France."

Russia has arrested and charged four men it believes carried out the attack at the 6,200-seat Moscow venue. It was the deadliest outrage the nation has endured for two decades.

France has a three-tier terror alert system, with the highest level triggered by an attack in France or overseas, or by the threat of an attack on French soil.

The highest alert makes it possible for the nation to introduce unusual security measures, including armed patrols in public places such as transport hubs and religious sites.

France had been on the middle-level terror alert since January but the level was likely to have been raised as the Olympic Games approached, with the high-profile event set to attract an estimated 15 million visitors to Paris between July 26 and Aug 11.

France's Interior Minister Gerald Darmanin recently said security concerns fed into the decision to issue only 326,000 tickets for the Olympic Games' opening ceremony, instead of the 1 million initially planned. The event will be held at an outdoor venue for the first time, instead of the usual indoor setting, which makes it much harder to control in terms of security.

Sky News said France has been the European Union nation most impacted by Islamist terrorism in recent years, with 82 attacks recorded between 1979 and May 2021 resulting in 332 deaths.