TEHRAN, Iran - About 100 students staged a rare protest Monday against Iranian President Mahmoud Ahmadinejad, calling him a "dictator" as he gave a speech at Tehran University marking the beginning of the academic year.

While the demonstrators and hard-line students loyal to Ahmadinejad scuffled in the auditorium, the president ignored chants of "Death to the dictator" and gave his speech on the merits of science and the pitfalls of Western-style democracy, witnesses said.

The hard-line students chanted "Thank you, president" as police looked on from outside the university's gates without intervening. The protesters dispersed after Ahmadinejad left the campus.

Students were once the main power base of Iran's reform movement but have faced intense pressure in recent years from Ahmadinejad's hard-line government, making anti-government protests rare.

The president faced a similar outburst during a speech last December when students at Amir Kabir Technical University called him a dictator and burned his picture.

Organizers hoped to avoid a similar disturbance Monday with tightened security measures. They checked the identity papers of everyone entering the campus and allowed only selected students into the hall for the speech, but the protesters were somehow able to gain entrance.