Anzhi Makhachkala have called on Lokomotiv Moscow to identify the supporter who threw a banana at defender Christopher Samba after Sunday's Premier League game in the Russian capital.
Anzhi released a statement condemning the incident on Monday, labelling it "idiotic".
The statement read: "We are deeply disappointed with the idiotic episode that happened to our player Christopher Samba after the match Lokomotiv-Anzhi.
"We are assured that the representatives of the football authorities, (the) security service of Lokomotiv will settle this issue and the guilty will be identified and punished."
Former Congo international Samba, who was born in France, added: "I'm very upset that such misconduct took place in view of children, who were sitting on those very stands.
"It can serve as a bad example for them. I try not to think about racism. I just want to believe that such problems do not exist on a global basis. Maybe I am mistaken but I do want to believe in it.
"As a rule any scandal of this kind is a result of a misconduct committed by one silly person. I don't want to react to this."
It is not the first time Anzhi have been involved in an incident of this kind. Last June a fan threw a banana at Brazilian left-back Roberto Carlos during a game with Krylya Sovetov.
He subsequently confessed but was not charged after insisting it was not a racist gesture.