(CNN) -- Chelsea officials have condemned chants from the English football club's own supporters during Tuesday's European Champions League match away to Belgian team Genk.
The chanting related to an incident involving Chelsea captain John Terry and Queens Park Rangers' Anton Ferdinand during an English Premier League match between the two teams on October 23.
Terry is being investigated by London police for alleged racial abuse against Ferdinand. The England captain is accused of using an obscene racial insult -- which has been widely repeated on fan forums thanks to widespread video footage on the Internet -- but denies doing so.
On Tuesday, Chelsea fans were heard to chant "Anton Ferdinand, you know what you are" during the Group E match at Genk's Cristal Arena. Terry was an unused substitute in the game, which ended in a 1-1 draw.
"The chanting was wholly inappropriate and we don't condone it," a spokesman for four-time English champions Chelsea said in a statement.
The west London club's Portuguese manager Andre Villas-Boas told a post-match press conference he had not heard the chants because he had been focused on the game.
"I was concentrating on the game," the 34-year-old said. British newspaper the Daily Telegraph reported that when Villas-Boas was informed of the incident, he responded: "I have nothing to say on that."
A British organization aimed at ridding the game of racism and inequality has called for Chelsea to apologize to anyone offended by the chants in Belgium, and for European football's ruling body to investigate.
"As with all incidents of abuse in European competition, it is under the jurisdiction of UEFA to determine whether action will be taken," Kick It Out chairman Herman Ouseley said on its official website.
"There is also a duty and obligation for Chelsea to do likewise. We'd urge the club to warn supporters of their conduct before future fixtures, look to identify who was involved, and apologize to Anton Ferdinand on behalf of supporters everywhere who found the chant deplorable."
Former Sunderland and West Ham defender Ferdinand gave a statement regarding the issue to the English Football Association on Monday.
"I have very strong feelings on the matter," the 26-year-old younger brother of England international Rio Ferdinand later said in his only public comment so far.
"But in the interests of fairness and not wishing to prejudice what I am sure will be a very thorough inquiry by the FA, this will be my last comment on the subject until the inquiry is concluded."
Terry, 30, issued his own statement immediately after the QPR match. He denied using a racial slur and claimed the issue had been a misunderstanding.
"I thought Anton was accusing me of using a racist slur against him," he said. "I responded aggressively, saying that I never used that term. I would never say such a thing, and I'm saddened that people would think so."