Some 4000 people, including students, dissidents, journalists and even former reformist officials, were arrested following street protests over suspected election fraud which led to President Mahmoud Ahmadinejad's re-election.

Whilst most of the protesters were detained in the Evin prison in northern Tehran, some 200 were transferred to the detention center Kahrizak in south of the Iranian capital - where several prisoners were reportedly physically abused and at least three killed.

The opposition cleric Mehdi Karroubi has also claimed that several young prisoners, male and female, were raped in Kahrizak.

Judge Mohammad Mossadegh ruled at the beginning of Tuesday's court session that it would be held in secret in the interest of national security and public peace.

The first court session was held with the victims' families and their lawyers as well as the defendants, the news agency said.

Iran's supreme leader, Ayatollah Ali Khamenei, who has the final say on all state affairs, ordered in July the closure Kahrizak due to lack of sufficient hygienic and other necessary standards for preserving detainees' rights.