Allegations of corruption in world tennis were reignited on Monday when a former Australian professional tennis player pleaded guilty to match-fixing just hours after a top global bookmaker suspended betting on a suspicious match at the Australian Open.

Betting agency Sportsbet noticed heavy gambling on a relatively minor match and suspended betting before alerting police.

Similar suspicious betting promoted Pinnacle Sports, a sports gambling company, to suspend bets on a mixed doubles match at the Australian Open on Sunday.

Unusually large amounts of money were placed on Andrea Hlavackova and Lukasz Kubot to beat Lara Arruabarrena and David Marrero, Pinnacle told the New York Times.

More than 12 hours before the match began, the heavy betting pushed the odds of a Arruabarrena and Marrero win down nearly 18 percent in the space of just 30 minutes, data from the sports odds comparison service Odds Portal shows.

Tennis regulators accept betting fluctuations can be an indicator of suspicious activity, but stress it is not sufficient to prove match fixing.

Nobody was immediately available to comment at Pinnacle or the Tennis Integrity Unit (TIU), the London-based body set up to counter corruption in the sport.

One tennis official, speaking on condition of anonymity, said betting on individual grand slam matches had been suspended on several occasions in the past but not one player had subsequently been found guilty of an offence.

Kubot said Monday that the TIU had asked him and Hlavackova questions about the match, without offering any more details. He added, though, that he didn't notice anything unusual on the court, saying "we give 100 per cent of that match" and he believed his opponents "were trying 100 per cent."

"It's not very comfortable to think that we didn't win the match on our terms," Hlavackova said. "We played our best [yesterday], we did very well and we won. So it's a bit not comfortable to be questioned if someone else was not playing 100 per cent or something."

Marrero and Arruabarrena rejected the allegations in an interview with the Times, with Marrero citing a knee injury for his team's poor play. They were not available for comment on Monday.

Tennis authorities have rejected reports by the BBC and BuzzFeed News, which said 16 players who have been ranked in the top 50 had been repeatedly flagged to the TIU over suspicions they had thrown matches in the past decade.

Former player pleads guilty

The case against former 187-ranked player Nick Lindahl reached court after reports surfaced last week that tennis authorities had failed to deal with widespread match-fixing, marring the opening of the year's first Grand Slam tournament.
 
Lindahl pleaded guilty in a Sydney court to one charge related to match-fixing in a minor 2013 tournament but will contest a separate evidence-tampering charge on technical grounds. Two other charges were dropped by prosecutors after the guilty plea.

Prosecutor Kate Young told the court that in September 2013, when playing at the Toowoomba Futures Tournament, Lindahl offered to intentionally lose a match to a lower-ranked player and informed an associate so that he could wager against him.

A transcript of telephone calls intercepted by police after the match and read in court appeared to show Lindahl coaching an associate on how to hide evidence from investigators and admitting to doing the same himself.

"Just get rid of it ... just get rid of everything," Lindahl said in the transcript, which was read by Young.

Lindahl, who was arrested a year ago, faces a maximum penalty of 10 years imprisonment on the charge to which he pleaded guilty and will be sentenced on April 15.

His lawyer, Troy Edwards, said the timing of the case coming to court amid a blaze of publicity about suspected match fixing and the Australian Open tournament was unfortunate.

"The matter was set to be heard before Christmas but there was a sick barrister and Nick asked me to agree to a delay," Edwards told Reuters. "And now it's all kind of blown up in his face."