Thousands have protested across the Middle East, North Africa and Asia against a film made in the US that depicts the Prophet Muhammad. What is in the film and why it has enraged so many people?
How did the film come to public attention?
The 14-minute video was first posted on YouTube on 1 July without attracting much attention. It was later picked up by various Arab TV stations, with religious Egyptian TV channel al-Nas' presenter Sheikh Khalad Abdalla broadcasting scenes on 8 September. A clip from his show, dubbed into Arabic, was posted online and within days had been viewed by hundreds of thousands of people.
The Afghan government says it has blocked YouTube to prevent people from watching it.
White House officials have asked YouTube to consider whether the film breaches its own guidelines. These guidelines include the stipulation: "We encourage free speech and defend everyone's right to express unpopular points of view. But we do not permit hate speech..."
Google, which owns YouTube, said in a statement that the video was "clearly within our guidelines and so will stay on YouTube", but added that "given the very difficult situation in Libya and Egypt" it had restricted access to the video in both countries.
The access to the video has also been blocked in Saudi Arabia, Indonesia and India.
What does the film show?
The footage, a trailer for a longer film entitled Innocence of Muslims (initial title was Desert Warrior), appears to depict Islam as a religion of violence and hate, and its Prophet Muhammad as a foolish and power-hungry man.
It opens with a scene in which a Coptic family in a newly radicalised Islamic Egypt is attacked by a group of Muslims while police look on without intervening. The father tells his daughters that Muslims want to kill all Christians and that the Islamic state is hiding their crimes.
It then shows the Prophet Muhammad and his life with his family and his followers in the desert. He is shown having sex with his wife Khadija and other women.
The video implies Khadija is behind the creation of the Koran, which is described as a combination of subversions of the Torah and the New Testament.
The trailer depicts Muhammad and his followers as killers, looters and extortionists. In one scene the Prophet sanctions the sexual abuse of children; in another, he says he is gay.
Why is it so offensive?
Depicting the Prophet Muhammad in any way already defies Islamic belief, let alone satirising him. His wife Khadija and his earliest companions are also revered in their own right in Islam, and so mocking these individuals is also considered serious blasphemy.
The founding principle of Islam is that the Koran is the direct word of God, revealed to Muhammad in order that he impart it to humankind. Depicting Khadija as planning to concoct a holy book out of the Old and New Testament defies an intrinsic Islamic belief.
Other references to allegations that Muhammad had affairs with women, was greedy and violent would clearly be insulting in any context.
What do we know about how it was put together?
The entire film is thought to be around an hour long, although most have only seen a 14-minute trailer which has now been widely circulated on the internet in English and Arabic.
The fuller version had a showing in a small Los Angeles cinema, the Vine Theatre, in June, where its title was The Innocence of Bin Laden.
It was clearly put together on a budget, with a cheaply made set, amateur actors and poor production standards. It was shot over five days at a California film studio in August last year, with a cast of around 50, together with a large production crew.
The most offensive parts of the film appear not to have been in the original, but dubbed over the soundtrack at a later date.
Who is Nakoula Basseley Nakoula?
The now infamous trailer for the film was posted through a Youtube account linked to the name "sambacile" - originally reported as an Israeli-born Jewish estate agent who had raised $5m (£3.1m) from Jewish donors in the US to make the film. But this person did not exist.
US authorities now say they have identified Nakoula Basseley Nakoula, an Egyptian-born Coptic Christian living in California, as the man who made the film.
Mr Nakoula, who was found guilty of fraud in 2010 and ordered to pay more than $790,000 in restitution, is thought to have used the pseudonym "Sam Bacile" to hide his identity. He denies the allegations.
Mr Nakoula is now in hiding.
What do the actors say about it?
They say they were misled about the film entirely, claiming that the original film had nothing to do with Islam or Muhammad, and that all references to him and insults to the religion were added post-production.
Cindy Lee Garcia, who had a small role in the film, told Gawker.com that she and others were given a script for a film and that it would be a historical drama set in the Middle East.
She is now suing Mr Nakoula, who she accuses of duping her into taking part in the "hateful" film. She is also asking a judge to order YouTube to remove the film from its site.
Who else appears to have been involved in the making of the film?
An American right-wing extremist called Steve Klein, linked with various anti-Islamic groups in California, has said he promoted the film but does not know the identity of the director.
According to Salon, Mr Klein cultivated links with Californian Coptic Christian Joseph Nasralla, who has been identified as president and CEO of Media for Christ, the organisation alleged to have produced the film.
Media for Christ is based in Duarte, California, and advertises its mission as promoting Christian values.
Pastor Terry Jones, from Florida, who gained notoriety after threatening to burn a copy of the Koran over plans to build an Islamic cultural centre near the site of the World Trade Center, has said he was in touch with a Mr Bacile over promotion of the film, but did not meet him and could not identify him.
According to Gawker.com, soft-porn director Alan Roberts was brought in to work on the film by Nakoula Basseley Nakoula. The site says he too may not have been aware what he was actually working on.
Is there something more going on here than protests about a film?
As was evident after Danish cartoons of the Prophet Muhammad were published in 2006, politicians and religious leaders in the region used perceived insults to Islam to rally public support.
Protests began to spread from Egypt to other countries - spurred on perhaps by local media - because of a long-standing mistrust and anger at the West, something a number of groups have been able to capitalise upon.
Middle East analyst Magdi Abdelhadi says that although the film will have caused genuine offence among many Muslims, groups like al-Qaeda, whose black flag has been seen at some of the protests, have seized the opportunity to stir up unrest.
Disillusionment, lack of opportunity and anger at the establishment is also feeding into the protests, analysts say.