Cuba's Yarelys Barrios who has been stripped of her Olympics silver medal.

An Olympics silver medal won by Cuba's Yarelys Barrios has reportedly been sold in an auction as the International Olympic Committee demands its return because of a doping violation.

Cuba's Barrios has been stripped of the medal she won in the discus at the 2008 Beijing Olympics after failing a doping re-test, the IOC said on Friday (NZ time).

The IOC also said that Qatari sprinter Samuel Adelebari Francis had also failed a re-test and had been disqualified from the men's 100 metres in which he finished 16th.

They have demanded the medals be returned.

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But that may not be so staright-forward.

Sportinglife.com reported that a silver medal was sold on the international auction website ebay for US$11,655 (NZ$16,000). The seller was a Cuban based in Canada, according to the report.

Barrios and Francis were among 98 athletes who have tested positive in reanalysis of samples from both the 2008 Beijing Games and the 2012 London Olympics.

The IOC ordered samples from the two Games to be re-tested using new techniques not available at the time of the competitions in attempt to root out cheating.

Six athletes, including three Russian medallists, were disqualified on Wednesday (Thursday NZT) from their events at the Beijing Games.

Barrios tested positive for the prohibited substance, acetazolamide, a diuretic and masking agent, the IOC said.

It said that the 33-year-old "has the silver medal, the diploma, and the medallist pin obtained in the discus throw event withdrawn and is ordered to return these".

It also added the governing body of athletics, the IAAF, to modify the results of the event and "to consider any further action within its own competence".

Barrios also competed at the 2012 London Olympics, where she was upgraded from fourth place to the bronze medal after Russia's Darya Pishchainikova was retroactively stripped of the silver for doping.

Francis tested positive for the banned substance stanozolol, the IOC said. He was also entered for the 200 metres but did not start.