Nine businesses, including a butcher, fishmonger, cheese shop and a McDonald’s, have had windows smashed and fake blood thrown on their walls in recent months.
Activists also spray-painted the slogan “Stop Speciesism”, a term denouncing unethical treatment of other species.
Five of the six detained people have since been or will now be released.
However, the Lille prosecutor’s office set a court date in December for a detained 21-year-old woman.
Tensions are high in the region after the port city of Calais reportedly cancelled a planned vegan festival on 8 September after learning of “a series of operations” by meat-eaters “aimed at stirring up trouble”.
A court in Lille ordered for it to go ahead, however, after complaints by organisers.
The vast majority of French people eat meat, with vegans representing a tiny percentage of the population.
According to a 2016 survey, only around 3% of French people are vegetarian.
But a number of recent incidents have sparked debate in a country that has a long culinary tradition of eating meat.
In March, a vegan activist received a suspended prison sentence for a Facebook post saying the killing of a butcher by an Islamist militant was “justice”.
The French Federation of Butchers wrote to the government asking for protection against militant vegans, saying they aimed to “impose on the immense majority of people their lifestyle, or even their ideology”.
The French government this year has introduced new regulations that ban vegetable-based food products in France from using words like “steak” and “sausage”.