The official IRNA news agency said six protesters went on trial, including Abdollah Momeni, a student leader.
IRNA later reported that the trial judge ordered that media should not name those being tried.
Iran has already put about 140 protesters on trial for contesting the re-election of Ahmadinejad in the June 12 presidential poll, which the opposition alleges was massively rigged.
Those charged include leading reformist politicians, activists and employees of the British and French embassies.
The opposition has denounced what it has called a "show trial."
The post-election unrest killed 36 people, according to Iranian officials, but opposition groups say 72 people died, some of them in police custody.