Croatian champions Dinamo Zagreb's chief Zdravko Mamic was detained here on Friday after making racial slurs against an ethnic Serb minister, police said.
Mamic was detained for questioning by Zagreb police after insulting Education Minister Zeljko Jovanovic, an ethnic Serb, whom he labelled "Croatophobe" in an interview to a local radio station.
Jovanovic "hates everything Croatian," Mamic told the Soundset radio, adding the minister was an "insult to the Croatian brain."
"When he looks at you, blood squirts from his eyes . Looking at his smile, one can only see eye-teeth ready for slaughter," Mamic said.
The comments could not have come at a worse time and risk stoking tensions ahead of Croatia's highly-charged World Cup qualifier with Serbia in Zagreb next Friday.
Serbs are Croatia's largest minority, making up around 4% of the country's population of 4.2 million.
Relations between Zagreb and its ethnic Serbs remain sensitive since the 1991-1995 war during which Serb rebels fought against the former Yugoslav republic's independence.
"As an (ethnic) Serb who never worked in education and sports (Jovanovic) cannot be in charge of the most important field in Croatia," added Mamic.
Local media reported that Mamic could be charged with inciting violence and hate speech. If found guilty he could be sentenced to up to three years in jail.
Mamic, known for his controversial behaviour and threats to journalists, is considered the most powerful man in Croatian football.
His statements were strongly condemned by the country's top officials, the Serb community here and the Croatian branch of the Helsinki Committee for Human Rights.
"The words that he (Mamic) used to personally insult the minister in the most vulgar and primitive way are also offensive and maliciously aggressive towards all members of the Serb minority (in Croatia) and Serbian people in general," President Ivo Josipovic said in a statement.
The Croatian Football Federation (HNS) said the statements by a member of their executive committee were "unacceptable."
The HNS said it would launch a disciplinary procedure against Mamic.
Respect for minorities' rights was a key condition set by the European Union for allowing Croatia to join the 27-member bloc. Croatia will join the EU on July 1.