"In the aftermath of the election, 4,000 people were arrested," judiciary spokesman Ali Reza Jamshidi told reporters.
He said 3,700 were released "very soon", but that "those who were involved in the riots were detained."
About 30 people were killed in the violence that flared during massive street protests against the re-election of President Mahmoud Ahmadinejad in the June 12 vote. Hundreds of top reformists, political activists and journalists were among those arrested.
At least 110 people have been put on trial before a revolutionary court in Tehran, including a French woman lecturer and two local employees of the British and French embassies, accused of involvement in the unrest.
