Iran's supreme leader, Ayatollah Ali Khamenei, on Thursday demanded the United States punish those behind an anti-Islam film blamed for sparking violent protests in the Middle East and North Africa.
"If the American politicians are honest that they had no role, then they must punish those who committed this heinous crime and their financial backers in proportion to this great crime," Khamenei said, according to a statement on his official website.
Earlier on Thursday, hundreds of Iranians staged a protest in Tehran over the amateur, American-made film which ridicules Islam's Prophet Mohammed.
The crowd chanted "Death to America!" and death to the movie's director, and an American flag was burnt.
But the rally, held near the Swiss embassy that handles US interests in the absence of US-Iran diplomatic ties, ended peacefully after two hours.
Security forces prevented the crowd from approaching the diplomatic compound.
Iranian news agencies said the demonstration was called by the Student Islamic Society, a hardline university group loyal to Khamenei that has held anti-Western rallies in the past.
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It was one of several protests in Middle East countries that happened on Thursday, following attacks on Tuesday on US diplomatic mission in Libya and Egypt by crowds whipped into a fury by the movie.
In the Libya attack, the US ambassador and three other US officials were killed.
A spokesman for Iran's foreign ministry, Ramin Mehmanparast, was quoted by the official IRNA news agency saying: "The killing of the American ambassador in Libya in protest over insults against the prophet of Islam is an example of Muslim hatred against the repulsive policies (of the United States), which are aligned with Islamophobia."
Khamenei was quoted on his site putting the blame on Israel and the United States.
"The number one accused in this crime is Zionism and the American government," he said.
The film at the centre of the outrage was made in the United States by a man initially reported by US media to be an American-Israeli who relied on funding from 100 Jews.
But subsequent reporting found that figure to be fictitious, likely invented by a Coptic Christian living in California and identified as Nakoula Basseley Nakoula. The film was being promoted by a Florida pastor, Terry Jones, known for previous Koran-burning stunts that angered Muslims in various countries.
US Secretary of State Hillary Clinton on Thursday condemned both the film -- saying "to me personally, this video is disgusting and reprehensible" -- and the violence seen in the protests.
She added: "The United States government had absolutely nothing to do with this video. We absolutely reject its content and message."