French anti-terror police on Tuesday arrested four men and one woman and seized weapons in raids just days before the presidential election run-off, sources said.
Some of the arrests were made in northern France, with two pistols and two machine guns found during one of the raids, a source close to the case said.
The weapons belonged to a man close to one of the suspects, who held the guns legally.
Some of the suspects were in touch on social media or the internet and some of their messages made authorities fear they were planning violent acts, the source added.
The arrests came nearly two weeks after 39-year-old Karim Cheurfi shot and killed a policeman on the Champs Elysees in Paris before being killed by police gunfire.
France votes on Sunday to pick its next president, with polling stations under high security after more than 230 people have been killed in a string of jihadist attacks in the country since January 2015.