Ligue 1 has condemned anti-gay chants made by some Paris Saint-Germain fans during the home game against Strasbourg on Saturday.
PSG are playing their bitter rivals next Sunday in Marseille, and the offensive slurs were made about the club and their midfielder Adrien Rabiot. The France international is a former PSG player who made more than 200 appearances for the club from 2012-19, and his move to Marseille has been seen as a betrayal.
"These latest discriminatory chants made by Paris Saint-Germain supporters are unacceptable when, at the same time, the whole of professional soccer has been working to ban homophobic behavior and chants from stadiums," the league said in a statement.
While the chanting was happening, the stadium announcer at Parc des Princes twice asked for the chants to stop and was jeered.
Ligue 1 has said its disciplinary committee would look into evidence.
Last season, some PSG players received a one-match suspended sentence by the league's disciplinary committee for offensive chants aimed at Marseille after a home league match.
Ousmane Dembélé, Achraf Hakimi, Randal Kolo Muani and Layvin Kurzawa were filmed using insults while celebrating at the end of a 4-0 win against Marseille. The four players issued apologies.
That match was also marred by anti-gay chanting by sections of PSG fans targeting Marseille players. As a result, the league ordered the closure of the Auteuil stand behind one of the goals for two matches, including one that was suspended.
PSG fans are banned from attending next Sunday's game in Marseille at Stade Velodrome for security reasons, with a history of clashes between rival fans.
The rivalry between the clubs has been one of the most vehement in French football since the 1990s, when Marseille was enjoying its heyday and PSG was becoming more ambitious with the backing of television broadcaster Canal Plus.
PSG have been bankrolled by Qatari investors QSI since 2011 and have become the most successful French club domestically with 12 league titles -- two more than Marseille and Saint-Etienne.
Although Marseille have not won the league since 2010, they still claim the ultimate bragging right over PSG as the only French club to have won the Champions League.