An American has been killed and at least one other wounded after militiamen stormed the US consulate in the Libyan city of Benghazi, officials say.
The building was set on fire after armed men raided the compound with grenades.
Protests have also been held at the US embassy in the Egyptian capital, Cairo.
In the attack in Benghazi, unidentified armed men stormed the grounds, shooting at buildings and throwing handmade bombs into the compound.
Security forces returned fire but Libyan officials say they were overwhelmed.
"One American official was killed and another injured in the hand. The other staff members were evacuated and are safe and sound," Libya's deputy interior minister Wanis al-Sharif told AFP.
The identity of the US official killed is not yet known. The consular worker was reported to have been shot.
The US Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film, 11 September 2012 No-one was said to have been in the building when it was set on fire
The film that sparked the demonstration is said to have been produced by a 52-year-old US citizen from California named Sam Bacile, and promoted by an expatriate Egyptian Copt.
The two men are described as having anti-Islamic views.
A trailer of the low-budget movie has appeared on YouTube translated into Arabic.
In Cairo, protesters breached the US embassy and tore down the United States flag, which was flying at half-mast to mark the 9/11 attacks, and replaced it with an Islamist banner.
Egyptian protesters condemned what they said was the humiliation of the Prophet of Islam under the pretext of freedom of speech.
"Both Muslims and Christians are participating in this protest against this offence to Islam," said one protester, according to the Associated Press.
The US embassy earlier issued a statement condemning "the continuing efforts by misguided individuals to hurt the religious feelings of Muslims - as we condemn efforts to offend believers of all religions".