An election propaganda poster at a polling station in the French capital Paris. (Source: Reuters)

The warning came as the election campaign entered its final week before the first round of voting, with Darmanin saying there could be "extremely strong" tensions and the French government was preparing for a "potentially explosive" situation.

President Emmanuel Macron, who shocked the country by dissolving parliament earlier this month, is not on the candidate list, but for many voters the election is seen as a referendum on the leader's fate.

According to AFP news agency, in a "letter to the French people" published on June 23, President Macron declared: "I trust you."

Acknowledging the “democratic malaise” in the country, President Macron wrote: “The next government, which will be reflected in your vote, I hope will be similar to the vote of many other Republicans who will show the courage to stand up to extremism.

You can count on me to act until May 2027 (the end of Mr. Macron's term - Editor's note) as your president, defender of the republic, of our values, respecting pluralism and your choices, serving you and the country."

The letter was used by the leader to try to shore up his coalition, which is lagging behind the far-right and a newly formed left-wing alliance in the polls, as the last hope for stability.

Recent polls show that Marine Le Pen's National Rally (RN) party will lead the early election with the first round set for June 30.