The raids were linked to a series of arrests in June during the European Championship soccer tournament that was held in cities across France, Interior Minister Bernard Cazeneuve said.
The arrests Sunday in Strasbourg and Marseille "allowed us to thwart a terrorist act that had been envisaged for a long time on our soil," Cazeneuve told reporters in Paris. Investigators are studying whether it was part of a larger plot to attack multiple sites simultaneously.
Cazeneuve didn't identify the target of the planned attack. The arrests came five days before the opening of the famed Christmas market in Strasbourg, which attracts tourists from across Europe and was the target of a failed extremist plot in 2000.
The suspects are French, Moroccan and Afghan, and are between 29 and 37 years old. Cazeneuve said six of them hadn't been known to intelligence services, and one was a Moroccan who had been flagged to France by a foreign government.
The raids in Strasbourg reportedly took place in the Neuhof and Meinau neighborhoods, where authorities dismantled a jihadi network in 2014 that included the brother of an Islamic State bomber who attacked the Bataclan concert hall in Paris last year.
French police have detained 418 people this year in terrorism investigations following deadly Islamic State attacks, Cazeneuve said.
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