Terrorism burst into the final week of the French presidential campaign after an "imminent" plot to attack a candidate was foiled, two men arrested and guns and explosives seized - reportedly thanks to a tip-off from British intelligence.

With five days to go before the first round of the most unpredictable presidential race in modern French history, agents and anti-terror police seized two suspects, Clément Baur, 23 and Mahiedine Merabet, 29, in Marseille, southern France.

The pair, one from Croix in northern France, the from the Val d'Oise near Paris, were arrested a few minutes apart in the 3rd arrondissement of the port city.

A black Isil flag, several weapons - including an Uzi submachine gun - and three kilogrammes of TATP-type explosives used in the Paris and Brussels suicide bombings were found in a subsequent raid, said Francis Molins, the Paris prosecutor.