Lens beat rival Lille (1-0) on Saturday in a derby from the North marked by incidents at half-time between Lensois supporters, who entered the lawn, and Lille.
These clashes caused the 30-minute delay in the kick-off of the second period, played under reinforced police surveillance.
Pole Przemyslaw Frankowski (73rd) scored the winning goal for the Sang et Or, who beat Losc for the first time since 2007.