FIFA has warned Mexico about the conduct of its fans after discriminatory chants at the Confederations Cup.

The anti-gay abuse was heard during Mexico's opening game against Portugal in Kazan, Russia, on Sunday, despite FIFA warning on the eve of the tournament that there would be tighter monitoring of offensive incidents in stadiums.

FIFA says its disciplinary committee chairman Anin Yeboah "decided to impose a warning on the Mexican Football Federation (FMF) for the misconduct of a small group of Mexican fans in relation to insulting and discriminatory chants."

Mexico fans direct the chant in question at opposition goalkeepers as they take goal kicks and first came under the international spotlight in Brazil 2014, when FIFA investigated it at the 2014 World Cup.

FIFA said before the tournament began that referees will have the power to abandon games in the face of discrimination from the stands.

But Mexico coach Juan Carlos Osorio, who is from Colombia, said he did not think the chant was discriminatory.

"There are certainly worse chants in other cultures that generate violence. It is a question of interpretation and has to be sorted out between the FMF and FIFA," he said.

"Some understand it as an outrage, an insult. Without being Mexican and being proud of managing this team, I think I understand the intent [of the chant] and it has nothing to do with [discrimination]."

Mexico has once again been warned by FIFA over its' fans goalkeeper chant. YURI CORTEZ/AFP/Getty Images

Mexico has previously been sanctioned over gay slurs by fans in the current World Cup qualifying campaign. A 30,000 Swiss francs ($30,600) fine in November was the fifth time in a year that FIFA acted against the chant in games involving Mexico.

The Mexican federation launched a campaign entitled "Embraced by Soccer" in March 2016 asking fans not to engage in discriminatory behavior, although the chant has continued at both national team and Liga MX games since.

FMF general secretary Guillermo Cantu told ESPN's John Sutcliffe that fans who continue to use the chant could be escorted out of the stadium with modern technology in the near future.

"What we are trying to achieve is that the chant could be eradicated from the stadiums where Mexico plays all over the world," he said.

"It's helpful for fans to know exactly what the consequences are, not only for the federation, but also personally for each fan. I think that will help because all we want to do is prepare well the team for each game and for the fans to enjoy each game."

Looking ahead to Mexico's second Confederations Cup game against New Zealand, Cantu said: "I hope that fans will be more educated over time.

"I think the first game helped because many of the Mexican fans actually stopped some of them who actually chanted and that's a good thing because now consciousness is more of a powerful weapon on this matter specifically."

Despite Osorio's objection to FIFA's warning, Cantu said the Mexican federation aims to be "respectful."

"We are part of a global federation," he said. "We are only one of 211 members and I think that education is something that we all need in order to understand the problem and really enjoy each game without getting a warning from anybody."

Information from The Associated Press was used in this report.