Russia 'concerned' by Sochi Olympics doping claim
The Russian authorities are "concerned" by new claims of doping among Russian athletes at the Sochi 2014 Winter Olympics, an adviser to Russia's sports minister says.
But Natalia Zhelanova added that whistleblower Vitaly Stepanov had "no connection to anti-doping activity".
Mr Stepanov, a former Russian anti-doping agency worker, made the claims on CBS network's 60 Minutes programme.
The World Anti-Doping Agency (Wada) pledged to act "immediately".
Mr Stepanov also alleged that undercover Russian intelligence agents had posed as anti-doping staff to cover up cheating at the Sochi Olympics.
He said he had been told of a cover-up by Grigory Rodchenkov, the former head of Moscow's anti-doping laboratory.
Reacting to the allegations, Ms Zhelanova told R-Sport website: "Of course, we are concerned by Mr Stepanov's statements but he has no connection to anti-doping activity."
"I would like to state that no-one has heard this from Mr Rodchenkov himself," she added.
Mr Rodchenkov was not interviewed by the CBS programme, which aired on Sunday.
However, Wada said it would now seek access to journalists' recordings of conversations.
The BBC and Wada have been unable to independently verify the allegations made in the programme, while Russia's sports ministry said it was "certain about transparency of doping control" in Sochi.
Russia won 13 gold medals at the Sochi Winter Olympics. The names of the alleged drug cheats were not revealed in the CBS programme.
Russian athletes have already been banned from international competition by the International Association of Athletics Federations (IAAF), the sport's world governing body, after a Wada commission report alleged "state-sponsored" doping in the country.