An Iranian exile website is reporting the country's main opposition leader has been hospitalized for heart tests.

Former presidential candidate Mir Hossein Mousavi has been under house arrest since widespread crackdowns in early 2011 after protests over the disputed re-election of President Mahmoud Ahmadinejad in 2009.

Thursday's report by Neday-e Sabz-e Azadi website says the former Green Movement leader underwent three hours of medical tests and is hospitalized for additional monitoring. The report cannot be independently verified in Iran.

Mousavi and fellow opposition figure Mahdi Karroubi have been effectively silenced by the clampdown on political dissent by Iranian authorities.