The International Association of Athletics Federations (IAAF), has announced that 28 athletes who competed at the 2005 and 2007 World Championships have been suspended after returning with “adverse findings” from retested samples.

The athletics world governing body has reacted to accusations in the media that it turned a blind eye to mass doping.

The IAAF said that the athletes are provisionally suspended and that none of the athletes concerned would be competing at the 2015 World Championships in Beijing, which gets under way on August 22.

It noted that a large majority of the athletes are retired with “very few” still active.

The IAAF said that from April 2015, it had again retested urine samples from Helsinki and Osaka, using the latest scientific developments and taking advantage of the new world anti-doping code’s provision to extend the period during which samples could be tested from eight to 10 years.

The IAAF said that these samples had been “proactively stored” at the Swiss Laboratory for Doping Analyses (LAD), the World Anti-Doping Agency-accredited laboratory in Lausanne, “in anticipation of new scientific developments”.

It pointed out that in 2012, it had already conducted a first round of reanalysis of samples taken from Helsinki, which it said had led to six adverse findings.

It said that to date, nine athletes had been sanctioned following retesting of samples from various World Championships.

There had been allegations that the results of 12,000 blood tests from 5,000 athletes between 2001 and 2012 showed an “extraordinary extent of cheating” by athletes at the world’s biggest events.

However, the IAAF responded by describing allegations of widespread doping in athletics as “sensationalist and confusing”.

The World Anti-Doping Agency’s independent commission is investigating the claims.