"It hasn't been an open court, either to the public or to the media."
The Fars news agency reported that a number of those appearing on Saturday were reformists who served in the government of Mohammed Khatami, a former president.
They included Mohammad Ali Abtahi, a former vice-president, Behzad Nabavi, a former industry minister and deputy speaker of parliament, and Abdollah Ramazanzadeh, a former government spokesman.
According to Fars, Abtahi said in his testimony that there had been no irregularities in the June 12 vote.
"I say to all my friends and all friends who hear us, that the issue of fraud in Iran was a lie and was brought up to create riots so Iran becomes like Afghanistan and Iraq and suffers damage and hardship," he was quoted as saying.
"If this happened, there would no name and trace of the revolution left."
Sustained domestic and international criticism of the crackdown prompted the authorities to free hundreds of detainees, but about 250 protesters are still being held.
Tehran insists that those accused of serious crimes would be brought to book.
The official IRNA news agency quoted prosecutors as saying that defendants include people whose photographs were taken while "committing the crimes".
"Some of their accomplices are on the run, but they will be surely identified by our dear people and handed over to the law," it said.
Mir Hossein Mousavi and Mehdi Karroubi, the two defeated pro-reform presidential candidates, have been pressing for the release of all detained protesters.
The disputed re-election has plunged the Islamic Republic into its worst political crisis in its 30-year existence.
About 20 protesters were killed in the protests that erupted across the country.
Although the authorities have largely succeeded in preventing further large-scale protests, the political upheaval is continuing with the opposition refusing to accept the legitimacy of Ahmadinejad's re-election.