French authorities found guns and bomb-making materials Tuesday after the arrest of two men suspected of plotting an "imminent" attack just days before presidential polls, sources close to the probe said.
The items were discovered during searches in the southern city of Marseille after the suspects -- "radicalised" Frenchmen aged 23 and 29 -- were taken into custody, sources said.
The sources asked not to be named because they were not authorised to speak publicly.
Interior Minister Matthias Fekl said the attack was to be carried out in the "next few days" as France gears up to vote on Sunday in the first round of a two-stage presidential election.
Last week, photos of the two suspects were distributed to the security teams for far-right candidate Marine Le Pen and centrist Emmanuel Macron.
"The photos were passed to my security service from Thursday," Le Pen told AFP, while an aide to Macron also confirmed his campaign team received the pictures.
Conservative candidate Francois Fillon was warned about the danger on Friday, an aide said.
France has been on high alert for more than two years following a string of terror attacks which began in January 2015, killing more than 230 people.
Polls have shown that voters are more concerned about unemployment and their spending power than terrorism or security, though analysts warn that concerns could change quickly in the event of further bloodshed.