The American ambassador to Libya and three other embassy staff were killed in a rocket attack after an armed mob protesting at a 'blasphemous' film about the Prophet Mohammed set fire to the consulate in Benghazi.
Sources told CNN that the attack on the embassy had been planned and attackers used the protest outside as a diversion - but could not say whether they instigated the protest or simply took advantage of it.
Secretary of State Hillary Clinton said a 'small, vicious group' carried out the attack, but it is not yet known who was behind it.
Christopher Stevens, 52, was at the compound evacuating staff when the building was attacked by 20 heavily-armed militants.
During a 20 minute fire fight, Libyan guards positioned inside the consulate managed to hold the attackers off as they sprayed the building with bullets before hurling a bomb inside.