September 14, 2012 -- Updated 0851 GMT (1651 HKT)
(CNN) -- The United States braced Friday for a fourth day of protests targeting its diplomatic facilities in the Middle East and elsewhere as furor in the Islamic world continued over a film that characterizes Prophet Mohammed as a womanizing buffoon.
Worries, in particular, stemmed from fears that calls for large, peaceful demonstrations on Friday, the traditional day of protest following the weekly Muslim prayer, would turn violent.
"We are in a full-court press at every single one of the posts in the Middle East and anywhere else there is any chance of demonstrations after Friday services to make sure nothing bad happens. And to have the security in place in case bad things do happen," one senior administration official said Thursday. The official, who was not authorized to publicly discuss the issue, spoke on condition of anonymity.
The ongoing unrest centers on an obscure 14-minute film trailer that mocks the Mohammed as a womanizer, child molester and ruthless killer. Posted in July on YouTube, the clip received attention after it was aired on Egyptian television and anti-Islam activists promoted it online.
On Tuesday, the same day people protesting the film stormed the U.S. Embassy in Cairo, the U.S. Consulate in Benghazi was attacked -- leading to the deaths of U.S. Ambassador Chris Stevens, State Department computer expert Sean Smith, and security officers Glen Doherty and Tyrone Woods, both former Navy SEAL commandos.
As word of video spreads, so do protests
People have taken to the streets in 11 nations and territories, including Egypt where protesters squared off Friday with security forces for a fourth day of protests near the U.S. Embassy in Cairo.
The film permit for "Innocence of Muslims" has been withdrawn at the request of federal authorities, who cited public safety concerns, according to Film LA, Inc., the non-profit agency that oversees production in the Los Angeles area.
By withdrawing the permit, copies of the film cannot be released by the agency.
Federal authorities have discounted as false a producer's claims to news outlets that he was an Israeli -- an assertion Israel's government denies -- who made the movie with financing with help from more than 100 Jewish donors.
The protests abroad and the false claim by the producer about Jewish donors caused the FBI and Department of Homeland Security to warn in a joint bulletin of a risk of an increase in violence both "at home and abroad as the film continues to gain attention."
Four days of unrest
Outside the U.S. Embassy in Cairo, riot police sporadically clashed with protesters for a fourth straight day after a failed attempt to disperse the demonstrators shortly after dawn on Friday.
Police armed with shields and batons, backed by an armed personnel carrier, rushed a group of several hundred protesters, a move that came after U.S. President Barack Obama warned that relations with Egypt will be shaped by how the country responds to the violence.
"I don't think that we would consider them an ally, but we don't consider them an enemy," Obama told Telemundo in an interview that aired Thursday night.
If Egypt takes actions, Obama said, that "indicate they're not taking responsibilities, as all other countries do where we have embassies, I think that's going to be a real big problem."
Authorities have arrested 37 people in connection with the violence, according to Egypt's state-run news agency.
A see-saw battle that began Thursday between protesters and the police raged through most of the night, with demonstrators throwing Molotov cocktails and rocks and authorities responding with tear gas.
Sporadic gun fire could be heard in the area around the U.S. Embassy.
At least 224 people were injured, according to Egyptian state television, Nile TV. Among the injured were 31 police officers, according to the Ministry of the Interior.
Here are the details about various protests:
--In Syria, hundreds gather outside the U.S. Embassy in Damascus. Protesters waved placards that condemned the film and blamed the the U.S. administration for allowing the production and broadcast of the film, according to the state-run Syrian Arab News Agency
--In Egypt, the Muslim Brotherhood called for a large, peaceful protest to denounce the film.
--In Iran, the Islamic Propagation Coordination Council called for nationwide rallies on Friday to protest against the film and what it is calling a U.S.-backed plot against Muslims, according to state-run news IRNA.
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 to prevent people there from watching the clips and staging violent protests. YouTube has already restricted access to the video.
Four arrested in Libya
Sources tracking militant Islamist groups in eastern Libya say the attack that killed Stevens and three other Americans was most likely carried out by a pro-al Qaeda group. Obama has vowed "justice will be done."
The first of two U.S. warships, carrying guided missiles, has arrived off the coast of Libya, and unmanned drones have been 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, said two U.S. officials, who spoke on condition of anonymity because they were not authorized to release the information.
About 50 Marines arrived in the country Wednesday, the officials said.
Four people have been arrested in connection with the attack on the U.S. consulate in Benghazi that left U.S. Ambassador to Libya J. Christopher Stevens and three other Americans dead, the president of the parliament's top aide said Friday.
Those arrested were not directly tied to the attacks that killed Stevens and the others, Monem Elyasser, the chief aide, told CNN by telephone.
Elyasser did not release the identities nor did he detail the allegations against the four people in custody.
During an interview on CNNI's "Amanpour" on Thursday, Prime Minister Mustafa Abushagur said there had been one arrest earlier in the day in Benghazi and three or four others who were being pursed.
"The evidence itself is based on mostly pictures that were taken around the compound at that time, and also through some witnesses," he said.
CNN's Arwa Damon, Ben Wedeman, Hamdi Alkhshali, Brian Walker and Elise Labott contributed to this report.
