Iranian Supreme Leader Ayatollah Khameini denied the Holocaust on Twitter, on March 21, 2014.

Iranian Supreme Leader Ayatollah Seyed Ali Khamenei on Friday questioned the reality of the Holocaust, on Twitter.

He wrote, “#Holocaust is an event whose reality is uncertain and if it has happened, it’s uncertain how it has happened.”

Twitter users were aghast.

Joel C. Rosenberg, New York Times best-selling author of thriller novels, including his latest, ‘The Auschwitz Escape,’ about the Holocaust explicitly, wrote: “Iran’s Ayatollah @khamenei_ir Tweeted his denial of the Holocaust this morning even as he prepares to bring about a Second Holocaust.”

Benny Avni, a journalist for the New York Post, Newsweek and Israel Radio, responded with the word “#Moderation,” in reference to Iran’s new posture as a “moderate regime.”

Pro-Israel blogger Elder of Ziyon wrote, “The Holocaust is orders of magnitude better documented than every single event mentioned in the #Koran. Just sayin’.”

“Pretty selective skepticism coming from someone who believes Muhammad literally flew around on a winged horse,” wrote another user.

Farrah, a Twitter user in London, wrote: “Seriously @khamenei_ir imma [I’m going to] have to unfollow you if you keep embarrassing yourself like this… #shame“.

The quote was taken from a speech given on Friday to thousands of pilgrims at the Shiite holy shrine of the 8th Imam, Hazrat Ali Ibn Moussa al-Reza, on the occasion of the Persian New Year, as reported by Lebanon’s Daily Star, based on an AFP report. AFP said his remarks were broadcast live from the northeastern city of Mashhad.

In the speech, Khamenei called for “resistance” in the face of a “cultural invasion” targeting the Islamic state’s religious beliefs.

In Europe, “no one dares to speak of the Holocaust, the crux of which is not clear if it is true, or if it were, how it was,” Khamenei said.

“Expressing opinion about the Holocaust, or casting doubt on it, is one of the greatest sins in the West. They prevent this, arrest the doubters, try them while claiming to be a free country,” he said.

“They passionately defend their red lines … how do they expect us to overlook our red lines that are based on our revolutionary and religious beliefs,” the Ayatollah said.

State media outlet Islamic Republic News Agency reported other chest beating statements, including, “That’s my word today: Iranian nation should make itself strong.”

“If a nation is not powerful, it will be subject to force; the world bullying powers will receive blackmail from it; they will trample upon it and invade and insult on it,” the Ayatollah said.