PARIS (AFP) - IOC president Thomas Bach said Wednesday that athletes and federations face life bans from the Olympics as he warned that doping has hit "an unprecedented level of criminality".

The International Olympic Committee leader also heightened pressure on Russia to clear up allegations of interference in testing at its doping laboratory during the 2014 Sochi Winter Games.

With 31 athletes from 12 countries already facing a ban from the Rio de Janeiro Olympics in August, Bach warned in a commentary in Le Monde newspaper of tough sanctions, including against individual federations, if the accusations against Russia were proved.

The allegations against the Sochi laboratory are "very detailed and therefore very worrying", Bach said.

"If the inquiry confirms that the allegations are true, this would be a shocking new scale of doping, with an unprecedented level of criminality," added Bach.

He said there would be "zero tolerance" against athletes and their entourage.

"This action could go from a life-time Olympic suspension to heavy financial sanctions, even the suspension or exclusion of whole national federations, as is currently the case with the Russian athletics federation."

With international doping scandals mounting, the IOC announced on Tuesday that 31 athletes from the 2008 Beijing Olympics had failed tests after their samples were re-examined.

Some 454 Beijing tests were re-examined and the results from 250 samples retested from the 2012 London Games will be announced shortly.