The chairman of the Turkish Athletics Federation has resigned in the wake of several doping scandals that have clouded Istanbul's bid for the 2020 Olympics.
"I thought it would be right that I step down," Mehmet Terzi, who has led the organization since 2004, said in a resignation letter published Thursday. "Unfortunately, it is a fact that so many anti-doping crimes were committed outside my and technical staff's control."
Terzi's decision follows a flurry of positive drug tests involving Turkish track and field athletes.
On Wednesday, the IAAF announced two-year bans for nine Turkish athletes, including two teenagers, who tested positive for anabolic steroids. Six of those cases involved field athletes testing positive for stanozolol at Turkey's national university championships held in May.
Earlier this year, the IAAF asked the Turkish federation to investigate Olympic 1,500-meter champion Asli Cakir Alptekin and two-time European 100-meter hurdles champion Nevin Yanit for alleged doping violations.
In June, eight Turkish athletes, including 2004 Olympic hammer silver medalist Esref Apak, were caught doping, and dozens reportedly failed targeted tests before the Mediterranean Games hosted by Turkey.
The doping cases come as Istanbul competes with Madrid and Tokyo for the right to host the 2020 Olympics. The host city will be selected by the IOC on Sept. 7 in Buenos Aires, Argentina.
Ugur Erdener, president of Turkey's national Olympic committee, said in a statement Friday that Turkey is "working aggressively and successfully to ensure that doping is eradicated completely from Turkish sport."
"There may be more positive tests to come, but it is a price we must pay to see clean young Turkish athletes winning medals on the international stage," said Erdener, who is also an IOC member and serves on the executive committee of the World Anti-Doping Agency.
No replacement for Terzi was immediately announced.
"I will ensure that the new leadership of the Turkish Athletics Federation abides by the rigorous standards set out in Turkey's comprehensive anti-doping legislation, other national laws and international anti-doping practices," Erdener said.