Russian President Vladimir Putin's spokesman has rejected claims that a former senior sports official participated in a state doping programme during the 2014 Winter Olympics in Sochi as a "defector's slander".
Spokesman Dmitry Peskov said in comments carried by state news agency TASS on Friday (local time) that the accusations, which included 15 doped medal winners, were "not based on any reliable information".
In an interview with The New York Times published on Thursday, Grigory Rodchenkov, a former director of a laboratory that tested Russian athletes for performance-enhancing drugs, said he helped provide such drugs to athletes and switch out drug-tainted testing samples with clean ones.
The World Anti-Doping Agency has said it will investigate the latest allegations, while a German Olympic official called for harshest sanctions and the French athletics chief proposed to ban the whole Russian team from the upcoming Rio de Janeiro Olympics if the allegations were true.
The Russian athletics team is already suspended after a report from a WADA commission, and it remains unclear whether they will be able to compete.
The allegations, along with a recommendation by the WADA foundation board to declare distance-running powerhouse Kenya non-compliant, and a French probe into payments around the election of the 2020 Games host city are casting a dark shadow over the Olympics 12 weeks ahead of opening ceremony in Rio.
The New York Times article was published during Thursday's WADA meeting, with the paper quoting Rodchenkov as saying Russian athletes submitted clean urine samples ahead of the Sochi Games which were then used to replace tainted samples taken during the Olympics via a hole in the wall of the laboratory.
The scheme reportedly involved athletes, officials and the secret service, and Rodchenkov told the New York Times it worked "like a Swiss watch".
He said he made a cocktail of three forbidden substances that Russian athletes used to boost their performance.
Russia topped the Sochi medal table with 33 medals, 13 of them gold.