The US ambassador John Christopher Stevens to Libya and three other embassy staff were killed in a mob attack on Tuesday in the Libyan city of Benghazi.
"The ambassador was killed along with three other officials," announced Wanis al-Sharif, the Interior deputy minister.
Stevens arrived to Libya as US ambassador in May, having served as the US special representative to Libya's National Transitional Council during the country's revolt last year against Muammar Gaddafi.
Stevens' death in Tuesday's attack was also confirmed in a tweet by Mustafa Abu Shagur, the deputy prime minister, who condemned the "cowardly act of attacking the US consulate and the killing of Stevens and other diplomats."
Asked about the deaths, a US Embassy employee in Tripoli said: "We have no information regarding this."The employee said the embassy could confirm the death of one person."
Protesters in Egypt and Libya attacked US diplomatic missions on Tuesday in a spasm of violence in response to a US film that they believe insulted the Prophet Mohammad (P.B.U.H).
Fawzi Wanis, who heads the High Security Commission in Benghazi, confirmed that Stevens was at the consulate when it was attacked.
Libyan officials, cited by AP, said that 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.
US Secretary of State Hillary Clinton, in a statement late on Tuesday, confirmed the death of one US diplomat, who was not identified, and condemned the attack on the Benghazi consulate, after a day of mayhem in two countries that raised fresh questions about Washington's relations with the Arab world.