"The objective of the conference is not to deny or prove the Holocaust. Its main aim is to create an atmosphere for thinkers to discuss freely the Holocaust," Iranian Foreign Minister Manouchehr Mottaki told the opening ceremony.

There was "no logical reason for opposing this conference," Mottaki said.

The conference, dubbed "Study of the Holocaust: A Global Perspective," was initiated by Iranian President Mahmoud Ahmadinejad, who had called the Holocaust, in which 6 million Jewswere killed, a "myth."

The Iranian Foreign Ministry's Institute for Political and International Studies (IPIS), which organized the conference, said 67 researchers from 30 countries would attend the meeting.

"Some people who had been asked to attend refused, saying it aims to deny the Holocaust. Others assumed the international conference was politically motivated and were reluctant to attend," IPIS chief Rassoul Moussavi said.

"Officials in charge of organizing the conference do not intend to deny or confirm it (the Holocaust). The duty of the IPIS is to create a suitable atmosphere for discussing historical issues," hesaid.

UN Secretary-General Kofi Annan has strongly opposed any attempt to question or deny the Holocaust, UN spokesman Stephane Dujarric said on Thursday, underlining that Annan will deeply deplore any conference whose purpose is to question or deny the reality of the Holocaust.

The conference has also aroused criticism from the United States and Germany.

U.S. State Department spokesman Sean McCormack said on Friday that "this meeting is really focused on highlighting those people who deny that there was, in fact, a Holocaust."

"In that regard, it's just yet another disgraceful act on this particular subject by the regime in Tehran," he added.

The German Foreign Ministry called in Iran's top envoy in Berlin on Friday in protest against the conference.

Other posters are challenging whether smoke ever rose from chimneys at Auschwitz.

Another poster make mockery of a film called 'Schindler's List' putting emphasis on deaths of Jews at the expense of ignoring war victims who were not Jews.

Some Jews taking part in the conference marched through the corridors sporting a flag of Israel with a big red line through it on their long black coats and the slogan "We are Jews, not Zionists" in Hebrew, Arabic and Persian.
"The reason we came here is to reveal to the world the misuse of the Holocaust by the Zionists," said one of their number, Rabbi Yisroel Dovid Weiss, who does not dispute the Holocaust itself.

"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 a mental rape," said Frederick Toeben, historian from Australian.

"It is my duty to be here, if we cannot speak freely it is a crime against humanity," said Toeben, who has served a prison sentence in his native Germany.

The conference emerges to say that the international community is expected to consider Hitler's crimes against humanity entirely rather than promote the 'myths' of the Holocaust, a clear discrimination against non-Jews.

Toeben brought along a huge model of the Treblinka extermination camp, complete with model trains and human figures which he said he would use to argue his claim that the gas chambers did not exist.

"Even some Western politicians have declared that the original foundation of the Zionist regime (Israel) was a mistake," he said on Saturday.

Ahmadinejad has said his questioning of the Holocaust is aimed at encouraging scholarly debate and an examination of the reasons behind the creation of the state of Israel.

Deputy Foreign Minister Manouchehr Mohammadi has said the Holocaust conference will look at issues such as "whether the gas chambers were actually used by the Nazis".

The conference has been condemned by various countries and organisations. U.S. State Department spokesman Sean McCormack described it as "disgraceful."

"It is just flabbergasting that ... the leadership of the regime continues to deny that 6 million plus people were killed in the Holocaust," he told reporters on Friday.

Karen Pollock, chief executive of the British Holocaust Educational Trust, called the Iranian conference "ridiculous".

"Denial of the Holocaust is a virulent form of anti-semitism," she said in a statement. "It is not only deeply offensive to Holocaust survivors but to any right-minded human being."

Iran was also sharply criticised for hosting a cartoon competition on the Holocaust this year.

The Foreign Minister, Manouchehr Mottaki, opened the Holocaust conference by attacking Western restrictions on "scientific and scholarly study". He said the West did not allow Holocaust denial because it would lead to questions "about the identity of the Zionist regime".

Rabbi Ahron Cohen, from Manchester, a member of Jews Against Zionism, said: "I and many others lost countless friends and relatives who perished by industrial genocide. It is a terrible affront to the memory of those who perished to belittle the guilt of those who committed this crime."

Above the conference hall was an exhibition of books, photographs and DVDs that largely supported the view the Holocaust did not take place or was much exaggerated. Photographs of the Holocaust were labelled "myth", with revisionist explanations labelled "truth". Books by the jailed historian David Irving were prominently displayed.

Mostafa Mohammedi, a Tehran University student who helped set up the exhibition, said: "Between 150,000 and 300,000 Jews died because of the natural causes of war such as famine and air raids. Unfortunately, Iranian schools still teach the official history dictated by the West, but we are campaigning to change that."

David Duke, the former Ku Klux Klan leader, said he was attending the confeence to defend freedom of speech. "We have a Holocaust mafia," said Mr Duke. "It's a shame Iran has to be the nation that calls into question that a world famous historian sits in prison for offering an opinion."

The Australian revisionist Fredrick Töben brought a model of the Treblinka death camp to prove the absence of gas chambers and said he faced arrest on his return.

An Iranian journalist outside the conference said: "It makes me ashamed, so ashamed."

Holocaust denier Bradley R. Smith of the US told participants he is convinced that "gas chambers never existed because otherwise famous politicians like Winston Churchill, Franklin D. Roosevelt or the pope [Pious XII] would have certainly spoken."

Robert Faurisson, a French professor who also denies the existence of gas chambers, addressed the conference Monday saying that it is "courageous and useful to establish the truth about something wich never existed."

"The courage of people like Mahmoud Ahmadinejad will allow the truth to emerge in the end and uncover this great lie which has influenced the history of humanity from World War II until today," he concluded.

Iran claims the conference, which opened on Monday and will end Tuesday, is aimed at opening a historic debate without preconceptions on the history of World War II while the West accuses Iranian leaders of denying the massacre of six million Jews. Iranian president Mahmoud Ahmadinejad has described the Holocaust as a "myth" and called for the destruction of Israel while rejecting charges of anti-Semitism.

Historians of the Third Reich, basing their figures on original Nazi documents, have estimated that approximately six million Jews were killed in the Holocaust. The regime of Adolf Hitler also killed millions of non-Jews.

Holocaust denial is a crime in a dozen European countries, including Germany and Austria, where British historian David Irving was jailed in February for three years for denying the Holocaust.

The foreign ministry had said that 67 foreign researchers from 30 countries were scheduled to take part. Among those speaking today are David Duke, the American white-supremacist politician and former Ku Klux Klan leader, and Georges Thiel, a French writer who has been prosecuted in France over his denials of the Holocaust.

Mr. Duke's remarks late this afternoon are expected to assert that no gas chambers or extermination camps were actually built during the war, on the ground that killing Jews that way would have been much too bothersome and expensive when the Nazis could have used much simpler methods, according to an advance summary of his speech published by the institute.

"Depicting Jews as the overwhelming victims of the Holocaust gave the moral high ground to the Allies as victors of the war, and allowed Jews to establish a state on the occupied land of Palestine," Mr. Duke's paper says, according to the summary.

One of the first scheduled speakers, Robert Faurisson of France, also called the Holocaust a myth created to justify the occupation of Palestine.

The conference is being held at the behest of Iran's president, Mahmoud Ahmadinejad, who likewise called the Holocaust a myth last year, and repeated a well-known slogan from the early days of the 1979 revolution in Iran, "Israel must be wiped off the map." He has spoken several times since then about a need to establish whether the Holocaust actually happened.

Most of the speakers at the conference today praised Mr. Ahmadinejad's comments.

Bendikt Frings, 48, a psychologist from Germany, said he believed Mr. Ahmadinejad was "an honest direct man," and said he had come to the conference to thank him for what he had initiated.

"We are forbidden to have such a conference in Germany," he said. " All my childhood, we waited for something like this."

Toben Feredrick, from Australia, said Mr. Ahmadinejad has opened an issue "which is morally and intellectually crippling the Western society."

"People are imprisoned in Germany for denying the Holocaust," he added.

Mr. Feredrick said he was jailed for six months in 1999 because of his ideas, and that a court in Germany has ordered him arrested if he speaks out publicly again denying that the Holocaust took place.

Other Western "revisionists" presented what they called new facts about the Holocaust at the conference, which also attracted attendees from some ultra-Orthodox Jews belonging to anti-Zionist sects that reject the state of Israel. One participant wearing the traditional long black coat and hat of such groups wore a badge saying: "A Jew, not a Zionist."

It was not entirely clear how the lineup of speakers at the conference was set. The Institute's website had invited scholars and researchers to submit papers in advance for consideration, but revealed little about how they were evaluated. The Iranian foreign ministry also provided little information about participants, saying that it feared they would be prosecuted by their home countries.

The conference included an exhibition today of various photos, posters and other material meant to contradict the accepted version of events, that the Nazis murdered millions of Jews and other "undesirables" in death camps during the war. New captions in Persian on some familiar photos of corpses at the camps argued that they were victims of typhus, not the German state.

Anti-Zionist literature, including a 2004 book by the American author Michael Collins Piper, about Zionist influence in America, was offered for sale to visitors at the conference. So, apparently, was a video recording of 12 Holocaust survivors telling their stories, suggesting that the views represented at the conference may not have been entirely one-sided.

The conference prompted outrage in the West. The German government summoned the Iranian charge d'affaires in Berlin to complain. The French Foreign Minister, Philippe Douste-Blazy, warned that the conference would be strongly condemned if it propagated claims denying the Holocaust.

Iran also organized an exhibition last summer of cartoons about the Holocaust, which outraged Jews inside Iran and out.

Iranian Jewish leaders reacted angrily to Mr. Ahmadinejad's Holocaust-denying comments last year, issuing a statement saying that his words were spreading fear among Jews in Iran.

"We consider the Holocaust as a fact and a disgrace for humanity," Haround Yashayai, a leading voice among Iranian Jews, said today. "We cannot say that such a conference cannot be held here. We have condemned similar events in the past, and see no reason to condemn it again."

In response to the students' slogans of "Down with Dictators,"Ahmadinejad said, "it is impossible to establish dictatorship in this country by the name of liberty."

"We have tasted dictatorship and our revolution has fought against it," the Iranian president said.

During his speech, some of the female students who were chanting slogans along with the male students, smashed the camera of Iranian state television to the ground, Fars said.

Some students even set Ahmadinejad's pictures on fire, Fars reported. In responding, the president said, "even if we were burnt for a thousand times, we will never step back even one centimeter."

The protesting students were confronted by pro-Ahmadinejad students, who began to chant "Ahmadinejad, we support you,"according to Fars.

The heckling prompted scuffles between the protesters and the president's supporters, who chanted: "Ahmadi, Ahmadi, we support you."

Mr Ahmadinejad, who was marking Iranian students' day, answered the "dictator" taunts by saying: "Everyone knows the real dictator is America and its servants." He added: "A few who claim there is a stifling climate are trying to stifle the majority by not letting them hear what is being said."

As students set fire to his picture, he said: "Everyone should know that Ahmadinejad is prepared to be burned in the path of true freedom, independence and justice."

Mr Ahmadinejad - who has turned his appearances before mass audiences into a potent political tool - has insisted that the protesters should not be punished, Reuters reported, citing a presidential spokesman.

The outburst came as Iranians prepare to go to the polls on Friday for elections to local councils and the powerful assembly of experts. It will be Mr Ahmadinejad's first electoral test since taking office and comes as his government is under pressure over rising prices and a perceived failure to deliver on economic promises.

The protest was also the latest in a series of recent signs of unrest on Iran's campuses, which had been largely quiet since the brutal suppression of a wave of pro-democracy demonstrations under Mr Ahmadinejad's reformist predecessor, Mohammed Khatami.

On Sunday, an estimated 700 Amir Kabir university students protested against a clampdown that has included the closure of the Islamic students' committee and the exclusion of former activists from courses. They were also demonstrating against the demolition of the students' committee building and the imposition of the university chancellor without elections. Police restricted access to the campus as demonstrators shouted anti-government slogans. Last week, hundreds of students at Tehran university - a traditional hotbed of political protest - were confronted by police as they chanted: "We only want freedom of expression."

Vahid Abedini, a member of the university's democracy seekers' committee, told the pro-reformist Etemad newspaper that the gatherings had been organised to defend the independence and freedom of universities.

Hundreds of students with a record of political activism have been barred from academic courses while many lecturers have been forced to retire.

This year, Mr Ahmadinejad demanded a purge of "secular and liberal" lecturers, whom he accused of having been a fifth column for western values and colonialism in Iran for the past 150 years. Under his presidency, a hardline cleric was appointed chancellor of Tehran university for the first time.

The remains of "martyrs" from the 1980-88 Iran-Iraq war have been given burial ceremonies in several universities in what has been seen as a pretext for allowing pro-government vigilantes entry to keep watch on student activities.