Libyan officials say the U.S. ambassador to Libya and three embassy staff were killed after a mob stormed the American consulate in the eastern city of Benghazi late Tuesday.

The deaths occurred when demonstrators angered over an amateur American-made film that insults Islam's Prophet Muhammad shot at and set fire to the U.S. consulate in Benghazi.

U.S. Ambassador J. Christopher Stevens, a career U.S. foreign service officer and one of the most experienced U.S. envoys in the region, had been in the country for less than four months after taking up his post in the capital, Tripoli, in May.

Deputy Interior Minister Wanis al-Sharif said the ambassador was killed “along with three other officials,” confirming that Stevens was at the consulate when it was attacked.

Sharif told reporters that an armed group attacked the premises in an “almost suicidal” mission. He said the U.S. mission is at “fault” for not taking adequate precautions.

There was no comment from the U.S. State Department or U.S. officials.

Earlier, U.S. Secretary of State Hillary Clinton had confirmed that only a single U.S. official was killed in the Benghazi attack, which she condemned “in the strongest terms.”

Clinton said some have sought to justify “this vicious behavior” as a response to inflammatory material posted on the Internet. She said the U.S. deplores any intentional effort to denigrate the religious beliefs of others, but rejected any “justification for violent acts of this kind.”

In Egypt, protesters scaled the fortified walls of the U.S. embassy in Cairo, tore up an American flag and replaced it with an Islamic banner. The demonstrators there – mainly ultraconservative Islamists – continued their protest action through the early hours of Wednesday.

The mobs were sparked by outrage over the film that U.S. media said was produced by Israeli-American Sam Bacile, who describes Islam as a “cancer,” and financed by expatriate members of Egypt's Coptic Christian minority group. Clips of the film in English and Arabic have recently been posted on YouTube.

The protests coincide with the 11th anniversary of the September 11th terrorist attacks in the United States.