Up to three armed men took hostages in the town near the border with Belgium, reports said.
One of the hostage takers was killed during the police operation, according to local officials.
The incident was not related to the security situation in France following the 13 November attacks in Paris.
Local authorities said the hostages were now in a "secure place"; at least one suspect had been arrested, according to reports.
Local media said the incident took place at around 19:00 local time (18:00 GMT), and an area of the town was cordoned off.
It is not clear how many people were held hostage.
Gunshots were fired, according to local residents.
The armed men had been planning a robbery targeting a banker, reports say.