Two Dinamo Zagreb senior officials have been arrested on suspicion of embezzlement and tax evasion.
Zdravko Mamic, the club chairman, and his brother Zoran, the team's coach, were held after deciding to return from the club's summer camp.
Croatian anti-corruption investigators claimed that a senior official with the Croatian Football Federation, a tax inspector and the Mamic brothers were suspected of giving bribes, tax evasion and other offences.
A statement on the Dinamo website said: "Dinamo's entire staff, the squad and all of the club's employees fully back them as we are convinced they will prove that they are innocent."
The club is the most successful in Croatia, having won 17 titles and claimed 10 successive league titles.
