More than 100 students scuffled with police and chanted "Death to the dictator" as the Iranian President, Mahmoud Ahmadin-ejad, made a speech at Tehran University.
There was also fighting and shoving between the protesters and rival students who shouted: "Revo-lutionary President, we support you."
Liberal-minded students and academics have criticised Mr Ahmadinejad for clamping down on dissent on campuses, although the President and his government insist they support free speech and welcome constructive opposition.
Yesterday's protest was the second rowdy reception Mr Ahmadinejad has received at a university in less than a year. In December, students tried to disrupt his speech on another campus by hurling firecrackers, chanting and burning his picture. "Students should feel responsible in the international arena ... Today's world needs them," state television quoted the President as telling university officials and students. The television bulletin made no mention of the disturbances outside the hall.
One of the pro-reform students said those allowed inside to listen were handpicked because they supported the President. "We were not invited," said the student, asking not to be named. Students and activists say some of those who have spoken out against the President in the past two years have been detained or blacklisted from university courses.
Students shouted: "Detained students should be released." Mr Ahmadinejad's supporters waved religious banners and shouted: "Hypocrites, leave the university."
The President, whose populist agenda and criticism of the West polarises opinion in Iran, had delayed his speech from last week because he felt unwell, officials had said.
Before leaving the campus, some professors gave Mr Ahmadinejad a carpet to thank him for his speech at New York's Columbia University last month. The head of the US university had introduced his guest as a "cruel dictator".
Mr Ahmadinejad swept to office in 2005 vowing to share out Iran's oil wealth fairly and a return to revolutionary ideals. Critics say his policies have stoked inflation and his fiery speeches have provoked Western nations to impose sanctions.
Gauging popular support is difficult in the absence of reliable opinion polls but Mr Ahmadinejad's backers were trounced in local council polls in December, particularly in big urban centres such as Tehran. His supporters face a new test in the March parliamentary election. Reuters