Libyan officials say the U.S. ambassador and three other embassy staffers have been killed in an attack on the U.S. consulate in the eastern city of Benghazi by protesters angry over a film that ridiculed Islam's Prophet Muhammad.

The officials, three in all, say Ambassador Chris Stevens was killed Tuesday night when he and a group of embassy employees went to the consulate to try to evacuate staff. The protesters were firing gunshots and rocket-propelled grenades.

The officials who reported the ambassador's death were Deputy Interior Minister for eastern Libya Wanis al-Sharaf; Benghazi security chief Abdel-Basit Haroun; and Benghazi city council and security official, Ahmed Bousinia.

"The American ambassador and three staff members were killed when gunmen fired rockets at them," a Libyan official in Benghazi told Reuters. Asked about the deaths, a U.S. Embassy employee in Tripoli said: "We have no information regarding this." The employee said the embassy could confirm the death of one person.

The Libyan official said the U.S. ambassador had been on his way to a safer venue after protesters attacked the U.S. Consulate in Benghazi and opened fire, killing a staff member, in protest at a U.S. film that they deemed blasphemous to the Prophet Muhammad.

The official said the U.S. Embassy had sent a military plane to transport the bodies to Tripoli to fly them to the United States.

Gunmen assaulted the Benghazi compound on Tuesday evening, clashing with Libyan security forces, who withdrew under heavy fire. The attackers fired at the buildings while others threw handmade bombs into the compound, setting off small explosions. Small fires were burning around the compound.

The assault followed a protest in neighboring Egypt where demonstrators scaled the walls of the U.S. Embassy, tore down the American flag and burned it during a protest over the same film which they said insulted the Prophet Muhammad.

It was the first such assaults on U.S. diplomatic facilities in either country, at a time when both Libya and Egypt are struggling to overcome the turmoil following the ouster of their longtime leaders, Moammar Gadhafi and Hosni Mubarak in uprisings last year.

The Wall Street Journal reported Tuesday that the film — titled "Innocence of Muslims" — was "directed and produced by an Israeli-American real-estate developer who characterized it as a political effort to call attention to the hypocrisies of Islam" adding that the movie had also been promoted by Terry Jones, the Florida pastor who has sparked deadly riots in the past by publicly burning copies of the Quran.

The Wall Street Journal reported further that the film's 52-year-old writer, director and producer, Sam Bacile, said that he had funded the movie with $5 million in donations from "about 100 Jews" whom he declined to identify. "Islam is a cancer," the paper quoted him as saying. "The movie is a political movie. It's not a religious movie."

The film was also being promoted by an extreme anti-Muslim Egyptian Christian campaigner in the United States. A 14-minute trailer of the movie that sparked the protests, posted on the website YouTube in an original English version and another dubbed into Egyptian Arabic, depicts Muhammad as a fraud, a womanizer and a madman in an overtly ridiculing way, showing him having sex and calling for massacres.

U.S. Secretary of State Hillary Clinton confirmed that one State Department officer had been killed in the protest at the U.S. consulate in Benghazi. She strongly condemned the attack and said she had called Libyan President Mohammed el-Megarif "to coordinate additional support to protect Americans in Libya."

Clinton expressed concern that the protests might spread to other countries. She said the U.S. was working with "partner countries around the world to protect our personnel, our missions, and American citizens worldwide."

"Some have sought to justify this vicious behavior as a response to inflammatory material posted on the Internet," Clinton said in a statement released by the U.S. State Department. "The United States deplores any intentional effort to denigrate the religious beliefs of others. Our commitment to religious tolerance goes back to the very beginning of our nation. But let me be clear: There is never any justification for violent acts of this kind."

The violence at the consulate lasted for about three hours, but the situation has now quieted down, said one witness.

"I heard nearly 10 explosions and all kinds of weapons. It was a terrifying day," said the witness who refused to give his name because he feared retribution.

Hours before the Benghazi attack, hundreds of mainly ultra-conservative Islamist protesters in Egypt marched to the U.S. Embassy in downtown Cairo, gathering outside its walls and chanting against the movie and the U.S. Most of the embassy staff had left the compound earlier thanks to early warnings of the upcoming demonstration.

"Say it, don't fear: Their ambassador must leave!" the crowd chanted.

Dozens of protesters then scaled the embassy walls, and several went into the courtyard and took the American flag off a pole. They brought it back to the crowd outside, which tried to burn it, but, failing that, tore it apart.

The protesters on the wall then raised on the flagpole a black flag with a Muslim declaration of faith, "There is no god but God and Muhammad is his prophet." The flag, similar to the banner used by al-Qaida, is commonly used by ultra-conservatives around the region.

The crowd grew throughout the evening with thousands standing outside the embassy. Dozens of riot police lined up along the embassy walls but did not stop protesters as they continued to climb and stand on the wall - though it appeared no more went into the compound.

The crowd chanted, "Islamic, Islamic. The right of our prophet will not die." Some shouted, "We are all Osama," referring to al-Qaida leader bin-Laden. Young men, some in masks, sprayed graffiti on the walls. Some grumbled that Islamist President Mohammed Morsi had not spoken out against the movie.

A group of women in black veils and robes that left only their eyes exposed chanted "Worshippers of the Cross, leave the Prophet Muhammad alone."

By midnight, the crowd had dwindled. The U.S. Embassy said on its Twitter account that there will be no visa services on Wednesday because of the protests.

A senior Egyptian security official at the embassy area said authorities allowed the protest because it was "peaceful." When they started climbing the walls, he said he called for more troops, denying that the protesters stormed the embassy. He spoke on condition of anonymity because he was not authorized to speak to reporters.

The Cairo embassy is in a diplomatic area in Garden City, where the British and Italian embassies are located, only a few blocks away from Tahrir Square, the center of last year's uprising that led to the ouster of Hosni Mubarak. The U.S. Embassy is built like a fortress, with a wall several meters (yards) high. But security has been scaled back in recent months, with several roadblocks leading to the facility removed after legal court cases by residents.

The Egyptian Foreign Ministry promised in a statement to provide the necessary security for diplomatic missions and embassies and warned that "such incidents will negatively impact the image of stability in Egypt, which will have consequences on the life of its citizens."

One protester, Hossam Ahmed, said he was among those who entered the embassy compound and replaced the American flag with the black one. He said the group has now removed the black flag from the pole and laid it instead on a ladder on top of the wall.

"This is a very simple reaction to harming our prophet," said another, bearded young protester, Abdel-Hamid Ibrahim.

In Washington, State Department spokeswoman Victoria Nuland said Egyptian police had removed the demonstrators who entered the embassy grounds.

Muslims find it offensive to depict Muhammad in any fashion, much less in an insulting way. The 2005 publication of 12 caricatures of the prophet Muhammad in a Danish newspaper triggered riots in many Muslim countries.

A YouTube spokesperson said the website would not take down the video at this point. The website's guidelines call for removing videos that include a threat of violence, but not those only expressing opinions. YouTube's practice is not to comment on specific videos.

"We take great care when we enforce our policies and try to allow as much content as possible while ensuring that our Community Guidelines are followed," the YouTube spokesperson said. "Flagged content that does not violate our guidelines will remain on the site."

Bacile, the American citizen who said he produced, directed and wrote the two-hour film, said he had not anticipated such a furious reaction.

"I feel sorry for the embassy. I am mad," Bacile said.

Speaking from a telephone with a California number, Bacile said he was Jewish and familiar with the region. Bacile said the film was produced in English and he doesn't know who dubbed it in Arabic. The full film has not been shown yet, he said, and he said he has declined distribution offers for now.

"My plan is to make a series of 200 hours" about the same subject, he said.

Morris Sadek, an Egyptian-born Christian in the U.S. known for his anti-Islam views, told The Associated Press from Washington that he was promoting the video on his website and on certain TV stations, which he did not identify.

Both depicted the film as showing how Coptic Christians are oppressed in Egypt, though it goes well beyond that to ridicule Muhammad - a reflection of their contention that Islam as a religion is inherently oppressive.

"The main problem is I am the first one to put on the screen someone who is [portraying] Muhammad. It makes them mad," Bacile said. "But we have to open the door. After 9/11 everybody should be in front of the judge, even Jesus, even Muhammad."

For several days, Egyptian media have been reporting on the video, playing some excerpts from it and blaming Sadek for it, with ultraconservative clerics going on air to denounce it.

Medhat Klada, a representative of Coptic Christian organizations in Europe, said Sadek's views were not representative of expatriate Copts.

"He is an extremist ... We don't go down this road. He has incited the people [in Egypt] against Copts," he said, speaking from Switzerland. "We refuse any attacks on religions because of a moral position."

But he said he was concerned about the backlash from angry Islamists, saying their protest only promotes the movie. "They don't know dialogue and they think that Islam will be offended from a movie."