Real Madrid midfielder Luka Modric has been questioned in Zagreb by anti-graft police in connection with a probe into Dinamo Zagreb officials suspected of bribery and tax evasion, local papers reported Thursday.

Modric, whose testimony is considered key for the case, was questioned on the financial details of his 2009 transfer to Tottenham Hotspur, the Jutarnji list daily reported.

The anti-graft prosecutors suspect that Dinamo Zagreb chief Zdravko Mamic illegally earned more than 6.9 million euros, through the transfer. Modric was questioned on Sunday, the paper reported.

Another Croatian international, Liverpool defender Dejan Lovren, was also to be questioned within the probe, it said.

Zdravko Mamic, his younger brother Zoran, the Croatian champions' coach, along with a top football federation official and a tax inspector are suspected by the national anti-corruption USKOK bureau of giving and receiving bribes, tax evasion and other offences.

The suspected criminal offences had been taking place since 2008.

The alleged offences cost Dinamo Zagreb and the state almost 15.5 million euros and two million euros respectively. The four suspects were all detained in July, and later released on bail.

Zdravko Mamic, considered the most influential man in Croatian football, has rejected the allegations against him.

The 56-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 of 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.