Referees, officials, agents and coaches at Belgium's biggest football clubs are being questioned after a major investigation into corruption.

The federal public prosecutor's office is looking into charges of fraud, tax evasion and money laundering, with Club Brugge and Anderlecht - the country's two biggest clubs - having their offices raided on Wednesday morning. These came as part of 44 raids nationwide and 13 more across France, Luxembourg, Cyprus, Montenegro, Macedonia and Serbia.

Agent Mogi Bayat, one of the most influential intermediaries in the Belgian top flight, has been arrested.

Bart Vertenten has been arrested. The Belgian referee officiated Celtic's Champions League qualifier in July (EPA)

Bayat has previously been a director at Charleroi but has, in recent years, become one of the most important cogs in the Belgian transfer machine. Another agent, Dejan Veljkovic, has been interviewed by police according to De Standaard.

Club Brugge coach Ivan Leko has been questioned by police while two referees - including the referee of Celtic's Champions League qualifier against Rosenborg earlier this season, Bart Vertenten - are also under interrogation.

"Club Brugge will give full cooperation to the investigation and has nothing to hide," club chairman Bart Verhaeghe told Flemish TV channel VTM Nieuws.

The federal prosecutor said a year-long probe into soccer shows evidence of "suspect financial operations" by sports agents and indications "of possible influencing of games" over the last season.

The statement said some soccer agents, independent from one another, "would have schemed to hide" transfer commissions, payments of players and coaches, and other payments from the Belgian authorities, causing tax losses.