A film trailer posted to YouTube that purportedly attacks Islam's prophet, Muhammad, has sparked protests against U.S. interests in Egypt and several other countries.

In Cairo, protesters climbed the walls of the U.S. Embassy on Sept. 11, 2012, bringing down the American flag and replacing it with a black flag with an Islamic inscription. Protests in Egypt have continued, and on Sept. 13 in Yemen, protesters scaled the U.S. Embassy wall before being forced to retreat. Similar protests have been reported in Iran, Tunisia, Morocco, Sudan and Gaza. Some countries, including Afghanistan, have blocked YouTube to prevent citizens from viewing the video.

In Libya, early reports indicated protests outside the U.S. consulate in Benghazi had escalated into violence, subsequently killing U.S. Ambassador Christopher Stevens and 3 other American personnel. On Sept. 12, U.S. officials said they believe the violence may have been a coordinated attack. - NBC News, The New York Times, AP, Reuters