Secret records for the Williams sisters and Simone Biles have been leaked online after “criminal” Russian hackers broke into the database which monitors athletes for drugs testing.

A cyber-espionage group published confidential documents about three of sport’s biggest female stars, warning it was “just the tip of the iceberg” of a planned wave of leaks of the records of competitors from last month’s Olympics.

The International Olympic Committee and World Anti-Doping Agency condemned the actions of a group the latter identified as Tsar Team (APT28), which aligned itself with the Anonymous network of online activists.

The hackers, nicknamed Fancy Bears, attempted to justify the publication by claiming it was exposing the scale of authorised drug use by athletes.