LONDON — A British newspaper reported Thursday that between six and 12 players entered into this year's men's singles draw at Wimbledon are being watched for match-fixing.

The Independent, citing an anonymous source, said the list includes Russians, Italians, Argentines and Spaniards, but did not reveal any names.

The International Tennis Federation would not comment on the report, and Jeff Rees, the head of the Tennis Integrity Unit at the ITF, was not available to answer questions.

The Independent also reported that a match between Oscar Hernandez of Spain and Daniel Koellerer of Austria from the Ordina Open in the Netherlands is being investigated because of unusual betting patterns, and a match from Kitzbuehel, Austria, last month is also "of concern." The paper reported that one match at the Monte Carlo Masters in April — Jean-Rene Lisnard's win over Christophe Rochus — led bookies to deny payments to winners.

Tennis has been hounded by match-fixing rumors since online betting exchange Betfair, in an unprecedented move, voided bets on a match in Poland in 2007 after fourth-ranked Nikolay Davydenko withdrew against 87th-ranked Martin Vassallo Arguello in the third set because of a foot injury.

In response to both the Davydenko match and other players speaking out about being approached by outsiders trying to influence a match, the ITF and other tennis governing bodies formed the Tennis Integrity Unit to keep the sport clean.

Since then, several players have been suspended or fined for betting on matches.

Wimbledon, arguably the most prestigious tennis tournament on the calendar, starts Monday at the All England Club.