FRENCH police have thwarted what they believe was a planned terror attack in the run-up to the presidential election and arrested two suspected radicals in the southern port city of Marseille.

The two men, Mahiedine Merabet, 29, and Clement Baur, 23, allegedly “intended to commit an attack on French soil in the very short term, which is to say in coming days”, Interior Minister Matthias Fekl said during a brief news conference.

France votes on Sunday in the first round of its two-stage election. Extra safety measures are being put in place for the ballot after extremist attacks that have made security one of the major issues of the presidential campaign.

The men, both French, are “suspected of wanting to commit, in an imminent way, a violent action on the eve of the French presidential election”, the Minister said.

He gave no details of targets or motives.

President Francois Hollande hailed the “remarkable” arrests and the work of police. Agents from the French domestic security agency, backed by elite police units, made the arrests.

France’s fight against home-grown and overseas Islamic extremism has been one of the main campaign topics for presidential candidates. Those on the right have been especially vocal, seeking to appeal to voters traumatised by Daesh-inspired attacks that have killed at least 235 people in France since January 2015.

With the terror threat “higher than ever”, Fekl said “everything is being done” to secure the election, the candidates, their election headquarters and rallies.

He said more than 50,000 police, gendarmes and soldiers will be deployed in France and its overseas territories on Sunday and for the decisive second-round vote on May 7.

Even before yesterday’s arrests, far-right candidate Marine Le Pen hardened her tone as voting approaches, promising to expel foreign extremists, freeze long-term visas and take back control of France’s borders. The Front National leader, who has campaigned against immigration and Europe’s open borders, also wants to impose a 10 per cent tax on labour contracts that go to foreigners and use reservists at the frontiers.