Christophe Galtier and Nice have strongly condemned chants from their supporters about the late Emiliano Sala.
Former Nantes striker Sala died in a plane crash in January 2019 as he travelled from France to the United Kingdom having signed for Cardiff City.
Sala was a hugely popular figure at Nantes, and supporters of the Ligue 1 club sang his name as they won the Coupe de France on Saturday. Nantes beat Nice 1-0 in the final.
But in Nice's first match since their defeat, sections of their home crowd in a 4-2 win over Saint-Etienne could be heard directing derogatory chants towards Sala.
Head coach Galtier was shocked by the abuse, revealing it was the focus of he and the Nice team after the match.
"I don't have words to describe what I heard," Galtier said. "One of the first reactions in the dressing room was not our songs, shouts of joy or relief. It was to talk about what the players heard.
"On behalf of my dressing room, my technical staff, my medical staff, the players, we would like to apologise to the family of Emiliano Sala and FC Nantes."
A Nice statement read: "OGC Nice condemns in the strongest terms the chant about Emiliano Sala heard on Wednesday evening at the Allianz Riviera.
"The club does not recognise its values or those of the entire red and black family in this unthinkable and abject provocation of a minority of its supporters.
"OGC Nice extends its support to the family and loved ones of Emiliano Sala."
Nantes, who beat Rennes 2-1 on Wednesday, also responded to news of the incident.
"I'm outraged," said coach Antoine Kombouare. "These people have no place in stadiums. They should be banned.
"It's shameful, I feel sorry for the family. I knew the fans could be stupid, but these are donkeys."
A Nantes statement added: "FC Nantes has discovered with horror the content of the chants of some OGC Nice supporters and can only strongly condemn such acts degrading the memory of Emiliano Sala.
"At the same time, FC Nantes would like to thank OGC Nice and its coach Christophe Galtier for their support and their firm condemnation of such remarks.
"FC Nantes as a whole supports Emiliano's family and loved ones."