SANAA/CAIRO - Demonstrators attacked the US embassies in Yemen and Egypt on Thursday in protest at a film they consider blasphemous to Islam, and the United States sent warships toward Libya, where the US ambassador was killed in related violence this week.
In Libya, authorities said they had made four arrests in the investigation into the attack that killed Ambassador Christopher Stevens and three other Americans in Benghazi on Tuesday.
US President Barack Obama, facing a new foreign policy crisis less than two months before seeking re-election, has vowed to bring to justice those responsible for the Benghazi attack, which US officials said may have been planned in advance - possibly by an al Qaeda-linked group.
Secretary of State Hillary Clinton said Washington had nothing to do with the crudely made film posted on the Internet, which she called "disgusting and reprehensible."
The amateurish production, entitled the "Innocence of Muslims," and originating in the United States, portrays the Prophet Mohammad as a womanizer, a homosexual and a child abuser.
For many Muslims, any depiction of the Prophet is blasphemous and caricatures or other characterizations have in the past provoked violent protests across the Muslim world.
Demonstrations spread further on Thursday, with US embassies again the targets of popular anger among Muslims questioning why the United States has failed to take action against the makers of the film.
Hundreds of Yemenis broke through the main gate of the heavily fortified US Embassy compound in Sanaa, shouting, "We sacrifice ourselves for you, Messenger of God." They smashed windows of security offices outside the embassy and burned cars.
A security source said at least 15 people were wounded, some by gunfire, before the government ringed the area with troops.