As many as 28 professional tennis players are being investigated for possible match-fixing offenses, with one player thought to be a Grand Slam star.
Spanish police arrested 83 people, including 28 professional tennis players, involved in "manipulation of professional tennis competitions", Europol said in a statement on Thursday.
None of the arrested people has been named.More news: Australia to Tour India in Feb-March: Full List of Matches, Venues
The arrests, which included one player who appeared at last year's US Open, follow an investigation into match-fixing by an organised Armenian criminal gang.
Some €167,000 (£151,000) in cash was seized along with a shotgun, more than 50 electronic devices, five luxury cars, credit cards and documents relating to the case in police raids on 11 properties. They also gave orders for "other members of the group" to place bets at the "national and global level".
"Our officers have proved the group had been operating since February 2017 and estimate that they had earned millions of euros through the operation", added the Civil Guard's statement.More news: Andy Murray to face Novak Djokovic in practice match before Australian Open
"Those now under arrest ran the money through different accounts before finally transferring it to those under their control, always using false names", said police.
The Guardia Civil, which carried out the investigation in conjunction with Europol and officials at the Spanish tax office, said that internet betting was a growing phenomenon and criminals who exploited it were priority targets for the force.More news: Is it too late to get a flu shot?