"Ninety-one suspects have been arrested by the police and their cases have been forwarded to the judiciary," Sadjadinia was quoted as saying by ISNA news agency. The anniversary passed off without any major anti-government protests, although some opposition websites and news agencies reported some skirmishes at Tehran's Sharif university between pro-regime hardliners and anti-regime students.
Last year on June 12, President Mahmoud Ahmadinejad was returned to power in an election that the opposition charged was massively rigged.
In the immediate aftermath of the poll, Tehran was rocked by massive street protests against him and clashes in which dozens of people were killed.
Street protests have subsided in recent months, but opposition leaders have vowed to continue their struggle against the hardliner.