Galatasaray accused Fenerbahce manager Jose Mourinho of racism and plan to take legal action after their 0-0 Super Lig draw.
He did not specify, but Mourinho said the home bench was “jumping like monkeys” and a Turkish referee would have ruined the match.
The game was overseen by Slovenian referee Slavko Vincic after both clubs requested a foreign official.
Galatasaray claimed on social media that Mourinho had made derogatory remarks about Turks since joining the league.
They stated that his comments had escalated to inhumane rhetoric and confirmed plans to file complaints with UEFA and FIFA.
Mourinho and Fenerbahce have yet to respond, though the coach has previously faced fines and suspensions for remarks about Turkish referees.
In the post-match press conference, Mourinho thanked Vincic, implying a Turkish referee would have officiated poorly.
He was also critical of the animated reactions from bench, suggesting that a Turkish referee might have penalized his team unfairly.
The controversy has intensified tensions between the Istanbul rivals, with legal action potentially setting a precedent.
The Turkish Football Federation and governing bodies may now be compelled to intervene as the situation unfolds.