Lens defeated reigning French champions Lille 1-0 on Saturday in a northern derby overshadowed by a pitch invasion that delayed the start of the second half by 30 minutes.
Dozens of Lens supporters stormed the Stade Bollaert-Delelis pitch at half-time to confront the visiting Lille fans nestled away in a corner of the ground after tensions flared with other spectators.
Riot police intervened to separate the factions of opposing supporters as both sets of fans hurled seats at each other over a partition wall.
The trouble comes the week after Nice were docked a point following the ugly incidents that led to their August 22 home match with Marseille to be abandoned.
That game will be replayed at a neutral venue on October 27. Nice were also ordered to play three matches behind closed doors.
"This start of the season is not going to help us. A reality check is quickly needed for everyone involved in football, starting with supporters," tweeted French sports minister Roxana Maracineanu.
Poland midfielder Przemyslaw Frankowski scored the winning goal on 74 minutes as Lens climbed up to second in Ligue 1, unbeaten through six games and three points adrift of Paris Saint-Germain, who host Lyon on Sunday.
Lille have won just once under new coach Jocelyn Gourvennec and lie 13th with only five points.