The US ambassador to Libya and three other embassy staff were killed in a rocket attack on Tuesday in the Libyan city of Benghazi, a Libyan official was quoted by Reuters as saying.
It was not clear if the ambassador was in his car or the Libyan consulate when the attack occurred.
"The Libyan ambassador and three staff members were killed when gunmen fired rockets at them," the official in Benghazi told Reuters
An armed mob protesting over a film deemed offensive to Islam attacked Tuesday the US consulate in Benghazi killing an American, hours after angry Islamists stormed Washington's embassy in Cairo.
Libya's deputy interior minister Wanis al-Sharif told AFP: "One American official was killed and another injured in the hand. The other staff members were evacuated and are safe and sound."
He could not say if the dead man was a diplomat.
"Demonstrators attacked the US consulate in Benghazi. They fired shots in the air before entering the building," said Sharif, who is in charge of the country's eastern region.
Abdelmonoem al-Horr, spokesman for the Libyan interior ministry's security commission, said rocket-propelled grenades were fired at the consulate from a nearby farm. Security forces and the interior ministry were trying to contain the situation, he added.
Witnesses said the attackers ripped up an American flag, then looted the consulate before setting it on fire on the eleventh anniversary of the September 11 attacks.
"Dozens of demonstrators attacked the consulate and set fire to it," said a Benghazi resident, who only gave his name as Omar, adding that he had seen the flames and heard shots in the vicinity.
Another Libyan witness said armed men had closed the streets leading up to the consulate, among them Salafists.
The violent protest was strongly condemned by Libya's General National Congress, which in a statement expressed "outrage at the unfortunate attack against the American consulate in Benghazi."
In Washington, State Department spokeswoman Victoria Nuland said: "We condemn in strongest terms this attack on our diplomatic mission."
US officials were working with the Libyans to secure the compound, Nuland said, adding that the earlier protest against the US embassy in Cairo, in which demonstrators scaled the walls, had now ended.
The Libyan incident came after thousands of Egyptian demonstrators tore down the Stars and Stripes at the US embassy in Cairo and replaced it with a black Islamic flag, similar to one adopted by several militant groups.
Nearly 3,000 demonstrators, most of supporters of the Salafist movement, gathered at the embassy in protest over a film deemed offensive to the Prophet Mohammed (Peace Be Upon Him) which was produced in the United States.
A dozen men scaled the embassy walls and one of them tore down the US flag, replacing it with a black one inscribed with the Muslim profession of faith: "There is no God but God and Mohammed is the prophet of God."
Egyptian police intervened without resort to force and persuaded the trespassers to come down. The crowd then largely dispersed leaving just a few hundred protesters outside the US mission, an AFP correspondent reported.
The Wall Street Journal reported that the film, “Innocence of Muslims’, was made by Israeli-American Sam Bacile, a 52-year-old real-estate developer from southern California.
The film is being promoted by controversial Florida pastor Terry Jones, who has drawn protests in the past for burning the Koran and vehemently opposing the construction of a mosque near Ground Zero in New York.
Arab League deputy secretary general, Ahmed Ben Helli, has condemned the film saying it "contained insults against the prophet Mohammed" and "was denounced by Christians and Muslims" across the Arab world.
Tuesday's protests came on the eleventh anniversary of the attacks of September 11, 2001, when US cities were targeted by hijacked planes.
Egyptian activist Wael Ghoneim wrote on his Facebook page that "attacking the US embassy on September 11 and raising flags linked to Al-Qaeda will not be understood by the American public as a protest over the film about the prophet.
"Instead, it will be received as a celebration of the crime that took place on September 11," he said.
Benghazi, a stronghold of Islamist extremists and cradle of the revolution that saw strongman Muammar Gaddafi captured and killed last year, has seen a wave of violence in recent months, including attacks on Western targets, bombings of military buildings and the killings of army and security officers.
Interior Minister Fawzi Abdelali has warned that Islamists amount to a "major force" in Libya both in terms of numbers and arms.
Anti-Islam filmmaker in hiding
A filmmaker based in California went into hiding after a YouTube trailer of his movie attacking Islam's prophet Muhammad (PBUH) sparked angry assaults by Muslims on U.S. missions in Egypt and Libya.
Speaking by phone Tuesday from an undisclosed location, writer and director Sam Bacile remained defiant.
"This is a political movie," said Bacile. "The U.S. lost a lot of money and a lot of people in wars in Iraq and Afghanistan, but we're fighting with ideas."
Bacile is a California real estate developer who identifies himself as a Jew.
The two-hour movie, "Innocence of Muslims," cost $5 million to make and was financed with the help of more than 100 Jewish donors, said Bacile, who wrote and directed it.
Though Bacile was apologetic about the American who was killed as a result of the outrage over his film, he blamed lax embassy security and the perpetrators of the violence.
"I feel the security system (at the embassies) is no good," said Bacile. "America should do something to change it."
A consultant on the film, Steve Klein, said the filmmaker is concerned for family members who live in Egypt. Bacile declined to confirm.
Klein said he vowed to help Bacile make the movie but warned him that "you're going to be the next Theo van Gogh." Van Gogh was a Dutch filmmaker killed by a Muslim in 2004 after making a film that was perceived as insulting to Islam.
"We went into this knowing this was probably going to happen," Klein said.
Bacile's film was dubbed into Egyptian Arabic by someone he doesn't know, but he speaks enough Arabic to confirm that the translation is accurate. It was made in three months in the summer of 2011, with 59 actors and about 45 people behind the camera.
The full film has been shown once, to a mostly empty theater in Hollywood earlier this year, said Bacile.
Egypt Islamists call for protests on Friday
Egypt's powerful Muslim Brotherhood on Wednesday called for nationwide protests Friday after a film deemed offensive to Islam sparked a deadly attack in Libya and furious protests in Cairo.
The Brotherhood calls "for peaceful protests on Friday outside all the main mosques in all of Egypt's provinces to denounce offences to religion and to the Prophet," the Muslim Brotherhood's Secretary General Mahmud Hussein said in a statement. He also urged all "national forces to join the protests."
French mosque desecrated
A mosque in the French city of Limoges has been desecrated by having human excrement smeared on its doors, Interior Minister Manuel Valls said Wednesday in a statement condemning the incident.
The attack occurred overnight following reports of mob violence in Egypt and Libya involving Islamists angered by a US-made film said to insult Islam.
There was no immediate indication however that the desecration was a reaction to or linked to the unrest over the film.
"This attack is a grave assault on the dignity of Muslims and is shocking for every citizen who upholds the values of respect and tolerance," Valls said in his statement.
The incident in Limoges, in the centre of France, came a month after two pigs heads were deposited at the entrance of a mosque in Montauban in the south of the country.
France is home to at least four million Muslims and leaders of the largest Islamic community in Europe say incidents of Islamaphobia are on the rise against a background of confrontation with the authorities.
Many Muslims have been angered by legislation banning women from wearing full veils and this year's elections were marked by debate over the use of halal methods of animal slaughter.
Afghanistan bans YouTube to prevent viewing film
Afghanistan banned the YouTube site on Wednesday so Afghans would not be able to watch a US-made film insulting the Prophet Mohammad (PBUH) that has sparked protests in Egypt and Libya and the killing of the US ambassador to Libya, the Ministry of Communications said.
"We have been told to shut down YouTube to the Afghan public until the video is taken down," Aimal Marjan, general director of Information Technology at the ministry, told Reuters.
In the past, material and actions deemed insulting to Islam have sparked deadly riots in Afghanistan.