France's Emmanuel Macron has ordered additional protection for critical infrastructure.
The French president says the threat to Europe from Russia's hybrid warfare has "intensified".
He adds any attack from Moscow on French soil will not go unanswered.
Emmanuel Macron says the threat posed by Russia's shadow operations is growing across Europe, as he orders measures to protect France's critical infrastructure from Russian "hybrid attacks".
The French president also said that Russia's attacks on French soil would not go unanswered, speaking after talks with presidential hopefuls and party leaders ahead of the April-May election.
The meeting with France's political leaders, held in the Elysee Palace's crisis room, was intended to brief attendees on confidential French intelligence assessments of the current security challenges.
Nicolas Lerner, head of France's foreign intelligence service DGSE, and Celine Berthon, head of France's domestic intelligence agency DGSI, attended.
Also present were more than a dozen presidential hopefuls and other senior politicians including centrists Edouard Philippe and Gabriel Attal as well as Jordan Bardella, head of the far-right National Rally party.
The National Rally's presidential candidate Marine Le Pen, who is leading in the polls, and hard-left Jean-Luc Melenchon were absent.
Since Moscow's full-scale invasion of Ukraine in 2022, Kyiv's European allies, including France, have raised the alarm about "hybrid attacks" linked to Russia.
The attacks have fallen below the threshold of open warfare, but have included drone flights near sensitive sites, airspace violations, and cyberattacks.
This month, Berlin blamed Moscow for an incident at Leipzig airport, which the European Union said bore all the hallmarks of "state-sponsored terrorism". The drone episode underscored an apparent escalation in the tactics Russia is willing to employ on NATO soil.
Mr Macron said he had ordered "the government to prepare a plan to protect our critical infrastructure" and the "most sensitive" defence industry and technology sites against drone and cyberattacks.
He added that France's interior minister had met regional prefects to step up vigilance.
Mr Macron said that despite the Russian threats, France would continue to support Ukraine and said that Paris would respond to Russia's shadow attacks.
"This will not go unanswered," Mr Macron said, without elaborating.
"We are not intimidated, because we know that what is at stake today in Ukraine is our security."
Berthon, France's top domestic spy, made an appearance at a business forum in August, saying the Leipzig incident signalled French companies could also be targeted.
Earlier this month a train carrying 186 passengers came off the rails in the northwestern French region of Normandy, injuring 44 people.
A rail fragment weighing around 300 kilograms was found on the tracks, officials said. While some politicians and police sources raised the possibility of sabotage, French authorities stressed the need for caution.