Hundreds of police have been deployed around Tehran University to prevent planned protests against President Mahmoud Ahmadinejad as Iran marks the annual Students Day on Monday, witnesses told AFP.
"Police have also cordoned off side lanes going towards Tehran university," a witness said.
Students Day observes the 1953 killing of three students by the shah's forces, just months after popular Iranian premier Mohammad Mossadeq was toppled with US backing.
The event this year is expected to be used by supporters of Iranian opposition leaders Mir Hossein Mousavi and Mehdi Karroubi to stage demonstrations against Ahmadinejad.
Opposition groups reject Ahmadinejad's re-election in the June 12 poll, saying it was massively rigged to ensure his return.
Iranian authorities have banned the foreign media from covering the expected protests on Monday and also reportedly cut Internet access in central Tehran.