The American ambassador to Libya is one of four US consulate staff killed in Benghazi following a rocket attack.
It is unclear whether Chris Stevens was in his car or the building when the rockets struck.
Witnesses say the compound in the eastern Libyan city came under attack by armed militia who were eventually forced to retreat by the Libyan army and American security guards inside.
The incident follows a protest in neighbouring Egypt, where demonstrators scaled the American embassy in protest at a US film promoted by an Egyptian Coptic Christian, which the protesters describe as blasphemous.
President Barack Obama and US Secretary of State Hillary Clinton have condemned the violence.The President denounced an “outrageous attack” and ordered increased security at U.S. diplomatic posts worldwide. “I have directed my administration to provide all necessary resources to support the security of our personnel in Libya, and to increase security at our diplomatic posts around the globe,” Obama said in a statement after the U.S. diplomats were killed in a rocket attack on their car in Benghazi.
“While the United States rejects efforts to denigrate the religious beliefs of others, we must all unequivocally oppose the kind of senseless violence that took the lives of these public servants,” he said today.