Sochi doping allegations could show unprecedented criminality - IOC

Russia is already at the heart of the biggest doping scandal in sport, with its track and field athletes suspended as a result of an investigation into allegations of widespread doping and their participation at this year's Rio Olympics in doubt.

Citing the former head of Russia's anti-doping agency, the New York Times reported last week that Russian anti-doping experts and members of the intelligence services secretly broke into tamper-proof bottles to replace urine samples tainted by performance-enhancing drugs with clean urine collected months earlier.

The Kremlin dismissed the allegations that Russia ran a sophisticated doping programme at 2014 Games at the Russian resort as treacherous slander, calling former agency head Grigory Rodchenkov "a turncoat".

The New York Times report was broadly consistent with accusations of the independent World Anti-Doping Agency (WADA) commission last November of widespread state-sponsored doping in Russia, which led to a ban on the country competing in international athletics competitions.

"Should the investigation (into Sochi) prove the allegations true it would represent a shocking new dimension in doping with an, until now, unprecedented level of criminality," Bach said in a statement.

"There can be no doubt - and no clean athlete in the world should have any doubt - that the IOC would react with its record of proven zero tolerance policy not only with regard to individual athletes, but to all their entourage within its reach."

Adding to the questions over doping, the IOC said on Wednesday up to 31 athletes could be banned from Rio 2016 following re-tests of doping samples from the Beijing Olympics in 2008. The IOC also ordered retests from Sochi and London 2012. The athletes are yet to be identified as tests of second samples are pending.

World athletics chiefs the IAAF meet on June 17 to discuss the participation of Russian track and field athletes in Rio and a decision will be announced after that.

Bach said Russian athletes would possibly need to prove they were clean if the scandal widened to include other sport federations, with the World Anti-Doping Agency conducting an investigation in Russia.

"The results of the WADA investigation will also greatly influence the nature of the participation of Russian athletes in the Olympic Games Rio 2016," Bach said.

"Should there be evidence of an organised system contaminating other sports, the international federations and the IOC would have to make the difficult decision between collective responsibility and individual justice."

"It would have to consider, whether in such 'contaminated' federations the presumption of innocence for athletes could still be applied, whether the burden of proof could be reversed."

Russia's Sports Ministry said on Wednesday it fully supported actions by the International Olympic Committee to bar athletes who dope from competitions, but said clean athletes should not be excluded from the Rio Games.