PARIS -- French anti-terrorism police have arrested seven people in Strasbourg and Marseille and thwarted what the interior minister called a new potential attack.

Interior Minister Bernard Cazeneuve, announcing the arrests Monday, said six of the suspects arrested hadn’t been known to intelligence services. Cazeneuve said that Sunday’s arrests prevented “a terrorist act that had been envisaged for a long time.”

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.

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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. It is Europe’s largest and oldest Christmas market.

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 of Iraq and Syria (ISIS) bomber who attacked the Bataclan concert hall in Paris last year.

French police have detained 418 people this year in terrorism investigations following the deadly ISIS attacks on the Bataclan and other sites in the French capital, Cazeneuve said.