Iranian state media say students have staged a demonstration at Tehran University, damaging the main gate.
The state-run IRNA news agency says the protesters Sunday chanted slogans against President Mahmoud Ahmadinejad and carried banners calling for the release of three fellow students.
The incident comes a day after intelligence agents arrested several people at Tehran University for allegedly planning an illegal demonstration.
State media quote Iran's Intelligence Ministry as saying Saturday that those arrested had entered the university using fake student cards. The ministry says anti-government groups had encouraged the suspects to come to Tehran University to create unrest.
Iran's Intelligence Ministry says agents confiscated several items from the suspects, including slings and rocks.
Iranian university students have held several rallies against President Ahmadinejad in recent months, accusing him of cracking down on dissent on campuses.
Some information for this report was provided by AFP and Reuters.