By Emmanuel Jarry and Sarah White
PARIS (Reuters) - Two men arrested in Marseille on Tuesday planned an "imminent and violent attack" ahead of the first round of France's presidential election on Sunday, authorities said.
"These two radicalised men ... intended to commit in the very short-term - by that I mean in the coming days - an attack on French soil," Interior Minister Matthias Fekl told a news conference.
Paris Prosecutor Francois Molins said in a news conference that weapons, explosives, videos and jidhadist propaganda materials had been found in the flat rented by French nationals Clement Baur, 23, and Mahiedine Merabet, 30, since April 1.
"A video intercepted on April 12 showed a machinegun placed on a table, with a daily newspaper from 13 March which had on its front page one of the presidential candidates.
"This morning the investigators managed to locate the apartment," Molins said, without naming the candidate.
France's internal intelligence agency had warned the main candidates of a threat, campaign officials said.
Comments by officials indicated that former prime minister Francois Fillon, centrist Emmanuel Macron and far-right leader Marine Le Pen were among those alerted to the risk.
France goes to the polls on April 23 and on May 7 in one of the most unpredictable elections in its modern history with security a key issue after attacks by militant Islamists which have killed more than 230 people in the past two years.
Molins said the Marseille suspects met in 2015, while sharing a prison cell for petty crime.
He said Baur had converted to Islam in 2007, was known to have had links with Chechen and Belgian jihadist networks and Belgian authorities had been investigating him.
A tip-off from another country had said Merabet was likely to carry out a violent act and was seeking to make contact with Islamic State, either to pledge allegiance to the group or ask it to claim responsibility for the planned attack, Molins said.
"The main candidates were warned in the middle of the last week that there was a risk and that two individuals had been identified. We received their photos and security of the candidates. Their meetings and headquarters were given extra protection," Macron's spokesman Benjamin Griveaux told Reuters.
Officials from Fillon's camp and Le Pen's National Front said they also had received word of a possible attack.
With the country still under a state of emergency, Fekl said 50,000 police, gendarmes and soldiers would be deployed for each leg of the election, and security reinforced for the candidates.
"Everything has been put in place to ensure the security of this big event for our democracy and our Republic. The security forces are mobilised everywhere across France to ensure the security of French people and to ensure the presidential campaign goes smoothly," he said.
Le Pen, one of the frontrunners in the race for the Elysee, is scheduled to hold the last big rally of her campaign in Marseille on Wednesday, according to her programme.
(Additional reporting by Matthias Blamont, Simon Carraud and Bate Felix; Writing by John Irish and Richard Balmforth; Editing by Andrew Roche)