Ahmadinejad was giving a speech to students at the Amir Kabir University, the scene of a protest the day before by hundreds of students to denounce a crackdown on a reformist-led university association.

“Some students chanted radical slogans and inflamed the atmosphere of the meeting,” said the semi-official Fars news agency, which is close to Ahmadinejad.

“A small number of students shouted ‘death to the dictator’ and smashed cameras of state television but they were confronted by a bigger group of students in the hall chanting: ‘We support Ahmadinejad’,” it said.

It was the latest in a series of student demonstrations in recent days, the first time in at least two years that such protests have taken place on this scale at Iranian universities.

Ahmadinejad, an ultra-conservative who won a shock election victory in 2005 on a wave of popular support, responded by describing those students chanting the slogans as an “oppressive” minority.

“A small number of people who claim there is oppression are creating oppression and do not let the majority hear (my) words,” he said.

In its late evening news report, state television said Ahmadinejad’s speech had been disrupted by some students and acknowledged that some of its news cameras had been damaged by the protestors.

It also showed pictures of a young man borne aloft as he burned a picture of the president and restive scenes as Ahmadinejad sought to make himself heard above a clearly noisy crowd.

The television also showed other students chanting their support for Ahmadinejad, punching their fists into the air and chanting “Death to America and Death to Israel”. Previously it has made no mention of the incident.

According to the student news agency ISNA, Ahmadinejad responded to the students’ chants of “students can die but they do not accept degradation” by lashing out at the United States.

“Today, the worst type of dictatorship in the world is the American dictatorship which has been clothed in human rights,” he said.

“Our students are free and they fight and die but do not accept the foreigners’ missions or bend to them,” he added.

“It is my honour to burn for the sake of the nation’s ideals and defend the system,” Ahmadinejad was quoted as telling the protesters who set fire his picture, ISNA said.

“Americans must know that even if Ahmadinejad’s body is burnt a thousand times for this purpose, Ahmadinejad will not retreat even a centimetre from these ideals.”

The Iranian president’s speech was also interrupted by firecrackers, ISNA said.

A group of Amir Kabir’s top students had earlier expressed objections to the government’s economic and political agenda as well as “confrontation with student activists and ridding universities of independent lecturers”.

“Bankrupting the country’s industry, inflation, distribution of poverty, defacement of the country’s international image and playing with the nation’s fate in diplomatic issues,” were among the points brought up in a statement.

“University is alive and criticises the government,” it added, according to ISNA.

Between 2,000 and 3,000 students also demonstrated at Tehran University on Wednesday to mark students’ day, chanting slogans such as “for freedom and against despotism”, ISNA reported at the time.