(CNN) - A wave of anger and outrage sparked by an obscure film clip spread to more Muslim countries on Thursday as protesters massed outside U.S. embassies in Africa and the Middle East.
The fallout comes in the wake of Tuesday's attack at the U.S. consulate in Benghazi, Libya, which claimed the lives of Ambassador Chris Stevens and three other consular officials. The deadly security breach happened on the 11th anniversary of the September 11 attacks and heightened tensions across the region.
The violence and protests stem from a 14-minute film trailer that mocks Islam's prophet. It was posted in July on YouTube, but got more notice after Egyptian television recently aired segments and anti-Islam activists promoted it online.
In response to Tuesday's attack in Libya, the United States deployed Marines to secure its interests in the region, as well as warships and drones to hunt for those responsible for killing the four American diplomatic staffers.
Here's the latest on the violence, the response, and the implications:
Since Tuesday's deadly assault in Libya -- and a protest the same day at the U.S. Embassy in Cairo, Egypt -- demonstrations, both small and large, have been reported in Israel, Gaza, Libya, Egypt, Yemen, Sudan, Tunisia, Morocco, Iraq, Iran, and among Muslims in the Indian-controlled region of Kashmir. Security has been heightened at U.S. diplomatic missions worldwide.
While some protesters say they have not seen any of the online film, they were incensed by reports of its depiction of the Prophet Mohammed.
One of the largest protests Thursday took place outside the U.S. Embassy in Cairo. One photo from Cairo shows a chalk drawing on the ground of a Jewish star with the words in Arabic, "Remember your black day 11 September." Demonstrators threw rocks and Molotov cocktails as police tried to disperse them by firing tear gas canisters.
At least 13 protesters and six police officers were injured, Egyptian government officials said.
The instability in Egypt is a primary concern to U.S. President Barack Obama, who warned in an interview with Telemundo that it would be "a real big problem" if the leaders in Egypt failed to protect American interests there.
Another massive protest took place Thursday in Sanaa, Yemen, where demonstrators breached a security wall at the U.S. Embassy as several thousand people protested outside.
Here are details about other protests:
-- In Tunisia and Morocco, protesters massed in front of U.S. embassies.
-- In Gaza City, Palestinians demonstrated outside U.N. headquarters, and about 200 Palestinians protested the film at the Palestine Legislative Council building. In one instance, Palestinian men burned a U.S. flag.
-- In Tel Aviv, Israel, about 50 people demonstrated in front of the U.S. Embassy.
-- In Sudan, the United States called on U.S. citizens on Wednesday to stay away from the embassy in Khartoum, where protests were going on.
-- Iranians protested near the Swiss Embassy in Tehran on Thursday. Switzerland represents U.S. interests in Iran, since Washington and Tehran do not have diplomatic relations. Up to 500 people chanted "Death to America!" and called for death to the director of the movie, which was made in the United States. The demonstration ended peacefully after two hours.
Anti-Islam film clip blamed, banned
So far, the violence has not spread to Afghanistan -- where there is a high potential for outrage to erupt into destabilizing chaos. Obama and his Afghan counterpart, Hamid Karzai, have expressed their commitment to prevent that from happening.
The Afghan government has ordered an indefinite block of YouTube, the online video-sharing website, to prevent people there from watching a clip of the anti-Islam film blamed for much of the fury bubbling over at protests in Islamic nations. YouTube has already restricted access to the video, which mocks the Muslim faith.
Numerous questions surround who made the film, which includes cartoonish scenes of Mohammed as a womanizer, child molester and ruthless killer.
Many Muslims find any depiction of Mohammed to be offensive -- a Danish newspaper's publication in 2005 of Mohammed caricatures triggered riots -- and derogatory depictions of the prophet are considered by some to be worse.
Response to ambassador's killing
Sources tracking militant Islamist groups in eastern Libya say Tuesday night's deadly attack was most likely carried out by a pro-al Qaeda group. Obama has vowed that "justice will be done."
Warships, carrying guided missiles, are on their way to the coast of Libya, and unmanned drones are being sent to help search for the killers.
A group of Marines called a Fleet Antiterrorism Security Team was deployed to Libya to help secure U.S. facilities, two U.S. officials said. About 50 Marines were headed to Tripoli and could deploy elsewhere in Libya after their arrival, the officials said.