Dinamo Zagreb chief Zdravko Mamic and his younger brother Zoran, the Croatian champions' coach, have been remanded in custody for a month after their arrest on suspicion of multi-million-euro bribery and tax evasion, the club said.

A Zagreb court judge decided that the two, who were detained on Saturday, were to stay in custody for a month to be prevented from influencing witnesses, a club statement said.

Dinamo labelled the decision "unfounded and odd" and stressed the club was "firmly standing behind" Zdravko and Zoran Mamic as it was convinced of their innocence.

The national anti-graft USKOK bureau suspects the two, along with a top official at the Croatian Football Federation (HNS) and a tax inspector, of giving and receiving bribes, tax evasion and other offences.

The alleged offences cost Dinamo Zagreb almost 118 million kunas ($17.3m, £11.1m, 15.5m euros) and the state some 12 million kunas.

The suspected criminal offences had been taking place since 2008, according to USKOK.

Damir Vrbanovic, the HNS executive president and a former Dinamo director, and the tax inspector were also ordered to be held for a month.

The Mamic brothers were detained at the Croatian border after returning from neighbouring Slovenia where they were with the players preparing for next season.

The move was made two days after police searched the homes of the Mamic brothers as well as the premises of Dinamo and the HNS.

But Zdravko Mamic, considered the most influential man in Croatian football, had labelled the allegations against him "absolutely pointless and constructed."

The 55-year-old Dinamo executive president said they were politically motivated and accused Prime Minister Zoran Milanovic of being behind them.

Mamic is a controversial figure well known for his outspoken behaviour and threatening journalists. Last year he was convicted of slander and ordered to pay 17,000 euros to a lawyer representing Brazil-born Croatian striker Eduardo da Silva.

In 2014, he was acquitted of inciting hatred with a slur against an ethnic Serb minister.