Iranian students have disrupted a speech President Mahmoud Ahmadinejad was giving at a university by lighting fireworks and burning his portrait.
Protests against the president are very uncommon in Iran
Mr Ahmadinejad responded calmly to protesters' shouts of "Death to the dictator", an official spokesman said.
The president reportedly described the hecklers as an "oppressive minority" and continued his speech.
Hundreds of students protested on Sunday against what they described as a crackdown on a students' association.
Protests against the government have become a rarity in Iran since Mr Ahmadinejad's election in 2005.
Monday's demonstration began when a group of some 50 students started chanting against the president as he addressed the Amir Kabir technical university.
A picture of Mr Ahmadinejad, held upside down, was set alight and firecrackers were lit.
According to Iran's students' news agency, ISNA, the president responded by saying: "Everyone should know that Ahmadinejad is prepared to be burned in the path of true freedom, independence and justice."
Reports say the president's supporters in the audience eventually drowned out the protesters with their own chanting.