Dozens of Iranian students burnt pictures of President Ahmadinejad and chanted “Death to the dictator” as he gave a speech at a university in Tehran yesterday.

Never has the hardline leader faced such open hostility at a public event, which came as Iran opened a conference questioning whether Nazi Germany murdered six million Jews.

One student activist said that the protest was against the “shameful” Holocaust conference and the “fact that many activists have not been allowed to attend university”. The conference “has brought to our country Nazis and racists from around the world”, he added.

Mr Ahmadinejad responded by saying: “Everyone should know that Ahmadinejad is prepared to be burnt in the path of true freedom, independence and justice”, according to an Iranian students’ news agency. He accused the protesters of being “Americanised”.

The protest during a speech at Amir Tabir University unrelated to the Holocaust meeting will be embarrassing for Mr Ahmadinejad. He has portrayed Iran as a champion of free speech in hosting the two-day Holocaust conference, which has attracted revisionist historians who have served jail sentences in Europe and David Duke, an American former Ku Klux Klan leader.

Almost 70 researchers from France to Indonesia arrived at the plush conference centre in an affluent north Tehran suburb. The centre’s walls were festooned with posters claiming to debunk “myths” of the Holocaust, disputing whether smoke ever rose from the chimneys at Auschwitz and denouncing the film Schindler’s List, which tells of the Nazi industrialist who rescued more than 1,000 Jews.

But the conference has embarrassed many ordinary Iranians who are aware of the damage such events are inflicting on their country’s image.

Some Iranians point out that they have much less freedom to debate pressing issues such as Iran’s nuclear programme, which has brought the threat of international sanctions. The conference, which has provoked international condemnation, was inspired by Mr Ahmadinejad himself, who has described the Holocaust as a myth invented to justify the occupation of Palestinian land. He has also declared that Israel should be “wiped off the map”.

The conference has dismayed Iran’s 25,000-strong Jewish community. Moris Motamed, Iran’s sole Jewish MP, said that denying the Holocaust was “a huge insult”.

Those at the conference included American and European rabbis from the fringe ultraOrthodox group Neturei Karta, whose theology holds that there should be no Jewish state until the Messiah arrives.

Ahron Cohen, a British rabbi, said: “We certainly say there was a Holocaust. But in no way can it be used as a justification for unjust acts against the Palestinians.” Welcoming the participants, Manouchehr Mottaki, the Iranian Foreign Minister, declared: “The aim of this conference is not to deny or confirm the Holocaust. Its main aim is to create an opportunity for thinkers who cannot express their views freely in Europe about the Holocaust.”

Georges Thiel, a French writer who has been convicted in France, where Holocaust denial is illegal, said that the Holocaust was “an enormous lie”: “Jewish people have been persecuted, that is true, they have been deported, but there was no machinery of murder in any camp — no gas chambers.”

Fredrick Toeben, an Australian who has served a prison sentence in his native Germany for inciting racial hatred, said: “Minds are being switched off to the Holocaust dogma as it is being sold as a historical fact and yet we are not able to question it. This is mental rape.”

He brought a model of the Treblinka extermination camp which, he said, he would demonstrate that the gas chambers did not exist.

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