Several aides to former Iranian President Mohammad Khatami and top reformists were put on trial on Tuesday on charges of masterminding the post-election unrest which rocked the Islamic republic.
"The fourth session of the revolutionary court dealing with masterminds of the recent incidents has begun," the Fars news agency said.
Iran has already staged mass trials of around 140 people on offences linked to the massive demonstrations and street violence that followed President Mahmoud Ahmadinejad's hotly-disputed victory in the June election.
The court proceedings, which opposition leaders denounced as "show trials," have angered the international community and heightened political tensions as Iran battles its worst crisis since the 1979 Islamic revolution.
Iranian media said those in the dock included Khatami aides such as former deputy interior minister Mostafa Tajzadeh, former deputy foreign minister Mohsen Aminzadeh, ex-deputy economy minister Mohsen Safaie-Farahani and reformist activists Mohsen Mirdamadi and Abdollah Ramezanzadeh.
Behzad Nabavi, a top reformist thinker and former minister in the post-revolution government of Ahmadinejad's main election rival Mir Hossein Mousavi, and Iranian-American scholar Kian Tajbakhsh were also on trial.