Libyan officials say the U.S. ambassador and three other Americans 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 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.

All of the officials -- three in all -- hold senior security positions in Benghazi.

They are deputy interior minister for eastern Libya Wanis al-Sharaf; Benghazi security chief Abdel-Basit Haroun; and Benghazi city council and security official Ahmed Bousinia.