Critics have denounced the court appearance as show trials
Six people have gone on trial in Iran for taking part in protests following June's disputed presidential election, a state news agency has reported.
It is the fifth trial brought against those accused of causing unrest and "undermining the Islamic government system" in the aftermath of the result.
One of the defendants is the student activist and human rights campaigner, Abdollah Momeni.
Opposition critics have denounced the court sessions as show trials.
More than a hundred people were put on trial in August.
Reformist former President Mohammad Khatami last month said trial confessions by moderates were made in "extraordinary conditions" and were invalid.
There were large-scale street protests following the announcement of the election result declaring the incumbent, Mahmoud Ahmadinejad, winner by a large margin. Iran was plunged into political turmoil.
The opposition claim the outcome was rigged, whereas hardliners have portrayed the protests as a foreign-backed bid to undermine the Islamic government system.
Iran's Spiritual Leader Ayatollah Ali Khamenei has insisted there was no election fraud.
He has also conceded he has seen no proof that opposition leaders blamed for the post-election unrest were agents of foreign powers.
Officials estimate that up to 36 people died in the clashes. The opposition say more than 70 people were killed.
In a separate development on Sunday, authorities freed Alireza Beheshti, a close aide to opposition leader Mir Hossein Mousavi.