The president of Columbia University, Lee Bollinger, delivered a strong rebuke to President Ahmadinejad of Iran during a question-and-answer program at the university today.

The university’s invitation to Mr. Ahmadinejad, who has called for the annihilation of Israel and said the Holocaust is “a myth,” has drawn outrage in New York and beyond and hundreds of protesters gathered at the campus to protest this morning.

Mr. Bollinger began by defending the university’s decision to summon President Ahmadinejad.

“This is the right thing to do,” Mr. Bollinger said, adding that he was sorry if the event hurt some people’s sentiments.

Mr. Bollinger called Mr. Ahmadinejad’s comments on the Holocaust “astonishingly uneducated” and characterized him as a “petty and cruel dictator.”

After a religious invocation, Mr. Ahmadinejad began his alloted 30 minutes by complaining that Mr. Bollinger made “many insults and claims that were incorrect.”

“I think the text read by the dear gentleman here, more than addressing me, was an insult to information and the knowledge of the audience here, present here,” Mr. Ahmadinejad said. “Many parts of his speech, there were many insults and claims that were incorrect, regretfully.”

After a speech, which drew heavily upon the Bible and Koran, the Iranian grew increasingly tense as he took tough questions from the assembly of 600 students and faculty members.

When asked whether he seeks the destruction of Israel, Mr. Ahmadinejad said, “We love all nations. We are friends with the Jewish people. There are many Jews in Iran, leaving peacefully, with security.”

Pressed for a yes or no answer, Mr Ahmadinejad said, “You asked the question, and then you want the answer the way you want to hear it. Well, this isn’t really a free flow of information.”

When challenged about the execution of homosexuals in Iran, Mr. Ahmadinejad said that Iran executes drug traffickers and killers, and drew a comparison with American capital punishment laws, eliciting applause from the crowd.

When pressed on the question, he said, “In Iran, we don’t have homosexuals, like in your country.” The response drew howls of laughter and booing. He continued, “In Iran, we do not have this phenomenon. I don’t know who’s told you that we have it.”

On the Holocaust, the Iranian leader said, “Why is it that the Palestinian people are paying the price for an event they had nothing to do with?”

Hundreds of protesters lingered outside the hall.

“This was an unimaginable mistake,” a leader of a Jewish Community Day School network called Ravsak, Marc Kramer, said. “Inviting him is a crime in it of itself.”

A member of Mothers Against Terrorism, Hillary Barr, stood outside the gates handing out postcards in support of sending American troops in Iraq.

One group of students arrived wearing yarmulkes and black t-shirts that read “Stop Ahmadinejad’s evil: Columbia Students Unite against Ahmadinejad.”

Others defended Columbia’s decision to invite the leader.

“I think he should be here. We need these questions out in the open,” a teacher who lives across the street from the university, Stephanie Rugoff, said.

A Columbia freshman who studies chemistry, Andra Nihali, said that in her homeland of Romania she could not imagine a debate like this.

“I think it’s a good thing. If he’s exposed to questions that challenge his beliefs, we’ll get a better understanding of Islam, and it can benefit both parties,” Ms. Nihali said.

Several of the students and faculty who packed the large windowless hall, Roone Arledge Auditorium on 114th Street and Broadway, said the national attention to the event sparked their interest in attending.

“It’s fun to feed off of all of this attention,” an audience member who procured a ticket through a friend who attends Columbia, Seth Aylmer, 25, said. “You can’t ignore that he’s a world leader. I think they should have invited him.”

Some students arrived with notebooks and pens. Others said they would just observe and hear what Mr. Ahmadinejad had to say.