On Monday, French Interior Minister Bernard Cazeneuve announced the arrests of six people for their alleged involvement in planning terror attacks, and said the detainees had not been known to the French intelligence services.
Cazeneuve further said the arrests, which were made overnight on Sunday, foiled “a terrorist act that had been envisaged for a long time,” without giving information on the target of the potential assault.
According to the premier, 43 people have been taken into custody in November alone as part of anti-terror operations following deadly Daesh (Islamic State) assaults in France over the past two years.
The news comes as Strasbourg has been on high alert over fears of attacks ahead of the opening of its Christmas market.
Local officials warned the market could be suspended or annulled if there were serious threats.
A state of emergency is still in place in France a year after attacks claimed by the Daesh group left at least 130 people dead in Paris.
In July, 86 people were killed when a truck rammed into a crowd in a southern resort in Nice. Daesh later claimed responsibility.
French intelligence services have warned recently that extremists might use new tactics by leaving explosive devices near sites that attract large crowds, especially those visited by foreign tourists.
They say the “new form of attack” could trigger huge casualties, while the perpetrator could escape unharmed.