According to a report by the World Anti-Doping Agency (WADA) due to be published Monday, the scale of doping corruption and money laundering within athletics dwarfs the scandal surrounding FIFA, the world’s football governing body.
"These are dark days for our sport,” Coe tweeted, after revealing the allegations had come as a complete surprise.
"I am more determined than ever to rebuild this sport and restore trust," the two-time Olympic 1500 metres gold medallist for Britain added.
Earlier this week, French police charged former IAAF chief Lamine Diack with corruption over suspicions he took bribes worth more than one million euros to cover up doping cases.
Coe confirmed he had not been in touch with Diack, whom he formerly praised as the “spiritual leader” of the IAAF when he won the election to succeed him.
The IAAF president also confirmed he had yet to see the WADA report, which is expected to be critical of both the IAAF and Russian athletics officials.
The IAAF has also launched official proceedings against one of Diack’s sons and three Russian athletics chiefs. They’re accused of blackmailing athletes suspected of doping, to let them keep competing, according to the WADA inquiry.