French authorities are investigating claims that a Red Star Belgrade official tried to fix the club's 6-1 Champions League Group C defeat at Paris Saint-Germain earlier this month.
UEFA warned France's National Financial Prosecutor's office (PNF) of possible manipulation of the result, and L'Equipe reported that the official in question was suspected of betting €5 million, via accomplices, on Red Star to lose by five goals.
PNF told The Associated Press on Friday that an investigation had been opened, but declined to comment further.
L'Equipe said UEFA had alerted PNF days before the teams played on Oct. 3.
It alleged that some Red Star players were talked into getting involved on the eve of the game, and said the official had a meeting with PSG chairman and CEO Nasser Al-Khelaifi scheduled that did not eventually take place.
"It was with the greatest stupefaction that PSG discovered this Friday an article on the L'Equipe website regarding suspicions of match-fixing concerning the Champions League game with Red Star Belgrade and suspicions regarding the alleged actions of bettors from Serbia," a PSG statement said.
"The club categorically rejects any and all direct and indirect implication in relation to these suspicions and would like to point out that at no moment has PSG been approached by the national financial court in charge of the investigation.
"PSG remains at the disposal of the investigators and will not tolerate the slightest attack on its reputation, nor that of its officials. To that end, the club reserves the right to take legal action against any party that makes defamatory statements against the club and/or its officials.
"The club reaffirms its profound attachment to the fundamental principle of sport, which is and always will be the integrity of its competitions."
Red Star responded to L'Equipe's report with "the highest amount of anger and disgust."
"The statements in this article seriously undermine our image and the club's reputation," the club said. "Current technology is so advanced that it is simply impossible that such a case cannot be resolved.
"The truth about this case will be established as soon as possible to ease suspicion about the involvement of one of our leaders in such dishonest activity."
Contacted by L'Equipe, honorary Red Star president Dragan Dzajic said: "This is the first that I have heard of it." Dzajic added that he knows "absolutely nothing about this -- it is not possible, it is untrue."
Red Star deputy spokesman Nebojsa Todorovic told Agence France Presse that he "cannot in any way comment on this," while Milan Vukovic, the spokesman for Serbia's football association, was unavailable for comment.
The French Regulatory Authority for Online Games, the body responsible for regulating online gambling in France, told L'Equipe no suspicious bets were made on the game.
"No anomalies were detected on the French betting market, nor in the partner countries of the Copenhagen Group [22 major European countries], nor via the Global Lottery Monitoring System," it said.