The World Anti-Doping Agency (WADA) said Stepanova's password was "illegally obtained," allowing unknown perpetrators to hack into her account on the agency's database - a system that stores information about athletes' locations for drug testing.

Stepanova, an 800-meter runner, blew the whistle in 2014 on widespread, state-sponsored doping practices in Russian athletics. Her testimony was a key factor that led to the suspension of the Russian athletics federation from the Summer Olympics currently underway in Rio de Janeiro.

The 30-year-old now lives in hiding at an undisclosed location in the United States. However, her whereabouts is likely listed in her WADA database account. WADA did not give information about what data was consulted in Stepanova's records. In a statement, the agency said only that its security monitoring had "noted that someone, other than Ms. Stepanova," had accessed her account.

"Unfortunately, like many organizations, WADA is not immune to attempted cyberattacks. Stakeholders can rest assured that the agency takes IT security and data privacy very seriously," it said, adding that law enforcement authorities had been contacted.

It said Stepanova's account had been immediately locked, and that there was no evidence other accounts had also been breached.

Stepanova was barred from competing in the Rio Games by the International Olympic Committee (IOC) because she herself had been part of the Russian doping system for several years. The decision came despite the fact that the ruling athletics body IAAF had granted her permission to run as a neutral athlete at events including Rio, owing to her "truly exceptional contribution to the fight against doping in sport."

The IOC considered banning all Russian athletes from the 2016 Games over doping allegations, but ultimately decided to leave the final decision to international sports federations.

nm/cmk (AP, AFP, dpa)