Porto have said they are "very surprised with the accusations" that their fans racially abused Mario Balotelli.
Manchester City have lodged an official complaint with UEFA after hearing monkey chants directed at Balotelli during the first half in their 2-1 victory in the Europa League on Thursday night.
UEFA is awaiting its match delegate's report before deciding whether to take action, but Porto spokesman Rui Cerqueira believes that the apparent abuse was down to a misunderstanding and that fans of both clubs were actually chanting "Kun, Kun, Kun; Hulk, Hulk, Hulk" in support of their players.
"What we can basically say is that nothing abnormal happened," Cerqueira said in the Daily Telegraph. "No one noticed anything strange, not even the UEFA delegates that worked closely with Porto during the match.
"We are very proud of having a multi-racial team, with players from all backgrounds and to have achieved many titles with respect. Porto players have never felt the slightest hint of racism and we were very surprised with the accusations."
Yaya Toure had said after the match that he had heard the chants.
''That's why we all like the Premier League, because it never happens there,'' he told Sky Sports News. ''Maybe in foreign countries they don't expect black players. I think in future it will be okay, they will change their minds and the game will become more open."