Dozens of students have scuffled with hardline supporters of Mahmoud Ahmadinejad on the Tehran University campus and chanted 'Death to the dictator' ahead of a speech there by the Iranian president.
The president was due to deliver a speech at the university later today to mark the start of the academic year.
Liberal-minded students and academics have criticised the president for clamping down on dissent on Iranian campuses.
When President Ahmadinejad was speaking at another university in December, he also faced students who sought to disrupt the speech by hurling firecrackers and burning his picture.
On that occasion, officials said the president reacted calmly.
The president, who tends to polarise opinion in the Islamic Republic by berating the West and with his populist agenda, was due to give a speech at Tehran University last week but officials said it was postponed because he was feeling unwell.
The president and his government insist they support free speech and constructive opposition, but students complain that some of those who have spoken out against the president have been detained or blacklisted from university courses.
