IAAF president Lord Coe says the athletics corruption scandal is not "bigger" than that facing Fifa in football, with both governing bodies under criminal investigation.
Lamine Diack, Coe's predecessor, is being investigated by French officials, and the bidding process to host the 2021 World Championships is also under scrutiny.
Fifa has also faced widespread corruption allegations this year.
Fifa president Sepp Blatter is the subject of a Swiss criminal investigation, started alongside a US inquiry which has indicted several top executives. Blatter denies any wrongdoing.
Asked if athletics' scandal was bigger than Fifa's, Coe said: "I don't actually believe that."
He told BBC Radio 4's Today programme: "I'm not walking away from the seriousness I'm confronting but we are talking about a criminal investigation that is looking at a handful of people.
"That's of no comfort to me because I'm still having to do the things I'm doing now on an hourly basis to make changes."
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The IAAF was implicated in an independent report by the World Anti-Doping Association, which examined allegations of doping, cover-ups and extortion in Russian athletics.
Russia's athletics federation has since been banned from competition until it complies with IAAF rules.
Diack is being investigated over allegations he took bribes to cover up positive drugs tests. He has yet to respond to the claims.
On Wednesday, the BBC learned French prosecutors were examining how the American city of Eugene was chosen as hosts for the 2021 World Championships.
Eugene is closely linked to sportswear giant Nike, for whom Lord Coe was an ambassador at the same time he was IAAF vice-president.
Coe, a former head of Fifa's ethics committee who took over as IAAF president in August, ended his 38-year paid ambassadorial role with Nike in November.
The decision to award the World Championships to Eugene was made without the usual bidding process, but Coe said: "That's not without precedence.
"We have selected cities before not within a bidding cycle. Eugene was not put forward by the IAAF. It was put forward by US track and field.
"My council decided that this was the best opportunity to get the World Championships into the United States."