Ukraine supporters have flooded FIFA's Facebook page with over 158,000 comments, most saying "Glory to Ukraine," after Croatia's assistant coach was fined for a video in which he used the same slogan.
FIFA hit Ognjen Vukojevic with a $15,000 fine and a warning for posting the clip, which also included Croatian defender Domagoj Vida, after they beat Russia in their World Cup quarterfinal on Saturday.
Both men have played for Ukrainian club Dynamo Kiev. Croatia's Football Federation later sacked Vukojevic from the national team's coaching staff.
Relations between Ukraine and Russia remain highly charged following Moscow's 2014 annexation of Ukraine's Crimea region and its backing for a separatist rebellion in eastern Ukraine. Some Ukrainian politicians even called on countries to boycott the 2018 World Cup.
By Tuesday afternoon, FIFA's Facebook page had over 158,000 reviews from users giving it the lowest one-star rating -- most less than 48 hours old and including the phrase "Glory to Ukraine!". Some added "Glory to Croatia!" and "Shame on FIFA!"
"Support for Russia means support for annexation and military aggression. Shame on you!" posted a user who gave his name as Vadim Ermilow from Kiev.
"Please answer my question: why can a football player not express his attitude towards what is going on in the world?" asked another user, Oleg Nazarov from Ukraine's Kremenchuk.
FIFA did not immediately comment on the posts.
Ukraine's national team did not qualify for the World Cup, but the country's football authority and some Ukrainian politicians have voiced support for Vukojevic, who FIFA said on Monday had apologised for his actions.
"'Glory to Ukraine' is a commonly used greeting in Ukraine ... (and) should not be interpreted as an act of aggression or provocation," the Football Federation of Ukraine said in a statement on Sunday.
Croatia face England in the World Cup semi-finals in Moscow on Wednesday.