Photo: Reuters

Mexico fans at the Confederations Cup in Russia have been told to stop provoking opposition goalkeepers with a homophobic insult.

A section of Mexico fans are in the habit of shouting 'puto' (vulgar term for male prostitute) as keepers take a goal-kick.

The Mexican Football Federation says that while they might find that funny, football's world body FIFA are distinctly not amused.

"The potential sanctions are heavy and if because of this behaviour we are stripped of a victory, or a match is stopped or you are excluded from a stadium we all end up losers," the federation warned their supporters via social media.

Mexico have been fined eight times for the chant during World Cup qualifiers since November 2015.

FIFA said on Tuesday it had warned Mexico after the chant was heard during their 2-2 draw with Portugal.

Observers have been placed by FIFA at Confederations Cup matches after they announced discriminatory behaviour from fans would be sanctioned.