President Emmanuel Macron said on Monday the gunmen who killed 137 people in a concert hall outside Moscow were part of an terrorist group that was behind foiled attempts to attack France over the past few months.
This, in turn, explains why the French government on Sunday increased the security alert to its highest level, Macron said.
Russia, which has challenged assertions by the United States that the Islamic State terrorist group orchestrated Friday's attack, continued on Monday to suggest Ukraine was to blame. Macron said this was "cynical and counterproductive."
"This attack was claimed by Islamic State," Macron said, "and the information available to us, to our (intelligence) services as well as to our main partners, indicates indeed that it was an entity of the Islamic State which instigated this attack.
"This group has attempted several times to hit France," he added, referring to Islamic State's affiliate in Afghanistan, which is known as ISIS-Khorasan or ISIS-K, which claimed responsibility for Friday's Moscow attack.
Terrorist attacks in France
France has been hit by a series of terrorist attacks over the past decade, the worst of which, in 2015, targeted the Bataclan concert hall and cafes and bars in Paris - which some Parisians said helped them understand why security would now be beefed up.
French officials were holding a meeting on Monday to look at specific measures to step up security, such as checking bags on entrance to concert halls or places of worship.
"It (the Moscow concert hall attack) brings to mind the Bataclan years, so yes, it's something that has left a mark in us forever," said IT worker Raffele Alegretti.
"So yes, I completely agree with the strengthening of the Vigipirate (public security) plan, because, in my opinion, people are a little worried," he said, pointing to the Olympic Games that Paris will host this summer.
"There has already been an attack during the Olympics (in Munich in 1972) ... Obviously, these are worrying events, in terms of security," said 25-year-old movie producer Lou Bardou-Jacquet.
Macron, who was speaking as he arrived for a visit in French Guiana, also said France had offered to increase cooperation with Russian intelligence services over the concert hall attack "so that we continue to fight effectively against these groups which are targeting several countries."
Russian President Vladimir Putin has not publicly mentioned Islamic State in connection with the attackers, who he said had been trying to escape to Ukraine. Russia has been at war with Ukraine since it invaded its neighbor in February 2022.
Putin said some people on "the Ukrainian side" had been prepared to spirit the gunmen across the border. Ukraine has denied any role in the attack and President Volodymyr Zelenskiy has accused Putin of seeking to divert blame for not securing Russia against such an attack by mentioning Ukraine.