The head of Iran's reformist Islamic Iran Participation Front party (IIPF) was released on bail, opposition websites reported Thursday.
Mohsen Mirdamadi was released Wednesday on a bail of 450,000 dollars, the websites said.
The IIPF supports the opposition Green Movement, led by defeated presidential candidate Mir-Hossein Moussavi, DPA reported.
Mirdamadi and the IIPF were among those who accused the government of election fraud in the June presidential polls and refused to acknowledge the re-election of President Mahmoud Ahmadinejad.
Mirdamadi was arrested after the June polls on charges of propaganda against the Islamic establishment and plans to topple the system.