Sources close to Iraqi Shi'ite leader Abdul Aziz al-Hakim say the cleric has died.
Hakim was being treated for lung cancer at a hospital in Iran, and those close to the man said his health was deteriorating.
A family member and an aide to Hakim, speaking on the condition of anonymity, separately told reporters Wednesday that he had suffered a setback.
Hakim was known for his close links with Iran, and he led the Supreme Iraqi Islamic Council, one of Iraq's most powerful Shi'ite groups.
In June, Iraqi President Jalal Talabani visited Hakim in Tehran, where the ailing cleric was seeking treatment.
Some information for this report was provided by AFP, AP and Reuters.