Paris - Police broke up a terror ring plotting an attack in France after arresting seven suspects in Strasbourg and Marseille over the weekend, Interior Minister Bernard Cazeneuve said onMonday.The arrests of the alleged plotters from France, Morocco and Afghanistan "enabled us to prevent a long-planned terror attack on our soil", Cazeneuve told a televised news conference. Investigators are trying to determine whether "the foiled attack was a co-ordinated attack aiming to target several sites simultaneously on our soil". Police raids were carried out overnight on Saturday in the eastern city of Strasbourg and Marseille in the south following an investigation by security services lasting more than eight months."Credible information made these arrests necessary," one security source told AFP earlier who was not authorised to comment on the case and spoke anonymously.The mayor of Strasbourg, Roland Ries, said the interior ministry had told him the targets were "in the Paris region" and not in his city, which will open a major Christmas market this Friday. France remains under a state of emergency that gives security forces enhanced powers to mount surveillance and launch raids, a year after attacks by jihadists on Paris that left 130 people dead.Security and fears about Islamic extremism are key issues in campaigning ahead of France's presidential elections due in April and May next year. "The threat of terrorism has never been so high on our soil," Cazeneuve said on Monday. "Zero risk cannot be guaranteed and anyone promising this is lying to the French people." He linked the latest suspects, aged from 29 to 37, to alleged extremists who were arrested shortly before the Euro 2016 football championship hosted by France in June and July.Only one of the detainees was known to security forces, a Moroccan who had been flagged by a "partner country", Cazeneuve said.Some members of the network are thought to have spent time in Syria, a security source told AFP. The interior minister said 418 people had been arrested for suspected links to terror networks since the start of the year.