A tip-off from British intelligence reportedly led to the arrest of two men in Marseille, southern France, on suspicion off planning an "imminent" terror attack just five days before presidential elections, reports The Telegraph.
Guns and bomb materials were found in a subsequent raid, a source close to the inquiry told AFP.
The two suspects, aged 23 and 29, were arrested on Tuesday morning by intelligence agents and elite anti-terror police in Marseille's 3rd arrondissement.
According to a source close to François Fillon, the conservative presidential candidate, cited by Le Figaro: "The initial intelligence came from British services who are thought to have captured data on two individuals known to security services."
Mr Fillon's team were warned last Friday and shown a photo of the two suspects. "Only François Fillon received tighter security" at that time, the source is cited as saying. Mr Fillon held rallies in Montpellier last Friday and on Monday in Nice, the scene of a deadly Islamic State group truck attack that killed 86 last July. Anti-terror police and snipers were present at the meetings.
According to BFMTV, police found a photo of one of the suspects standing in front of an Islamic State group flag and holding a machine gun and a copy of Le Monde with Mr Fillon on the cover.
Police, who had been hunting the pair since the end of last week, seized the suspects a few minutes apart in the southeastern port city, a police source told Reuters.
The police source said the two men appeared to have turned to radical Islam during a term in prison. A search of a rented apartment was underway.
French police opened an anti-terror inquiry into the oldest of the two suspects on April 5th. According to BFMTV, the man from Croix, in northern France, was previously known to police for armed robbery. He had been under surveillance since labelled as radicalised and his premises had been searched in autumn 2016.
Five days later, a second inquiry was launched into the second suspect, from Ermont in the Val-d'Oise near Paris. "As the inquiry proceeded, it emerged that the pair were working on the same project," a source closer to the probe told the channel.
While there has been no confirmation of their suspected targets, Marine Le Pen, the far-Right Front National candidate will hold what may be her last campaign rally in Marseille on Wednesday night.
The teams of Ms Le Pen and Emmanuel Macron, the centrist frontrunner, received photos of the two suspects ahead of their arrests last Thursday, they confirmed. Ms Le Pen's camp pointed out that the UOIF, an umbrella French Muslim group, had singled her out as "the candidate to beat".
Matthias Fekl, the French interior minister, said that two individuals were arrested in the 3rd arrondissement "suspected of wanting to launch an imminent violent act on the eve of the presidential elections".