Diack told the International Olympic Committee that the International Association of Athletics Federations (IAAF) would answer the allegations made by German television channel ARD and British newspaper the Sunday Times.
"Behind all this there is a desire to redistribute medals, take care of this," Diack, who will stand down as IAAF president this month, told IOC members.
ARD and the Sunday Times obtained a database of 12,000 tests taken on 5,000 athletes. Experts who studied the material said one third of athletics medals in endurance events at world championships and Olympics between 2001 and 2012 had given suspicious tests.
"Our office is working and is going to answer all these questions," he added. The IAAF has promised a statement on the allegations.
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"Emminent experts have concluded that from 2001 to 2012 hundreds of medals were wrongly given. We will not comment."
Diack said he would "calmly" let the IAAF bureau study the allegations.
"Behind all this is a desire to redistribute medals, take care of this."
Adam Pengilly, a British member of the IOC, called on the IAAF to "promote" clean athletics.
"They seem to have been quiet in the past year," about major accusations over doping in Russia and world athletics, Pengilly told the IOC meeting.
IOC president Thomas Bach said that while allegations are being handled by the IAAF "I don't think this is something to do with the IOC or the IOC president," despite Olympic events being involved.