Violence has erupted in central Sydney as hundreds of Muslims protest against a controversial film about the Prophet Mohammed.
It is the latest in a series of demonstrations that have killed at least six people in the Middle East. Protestors have also marched through London.
The wave of protests spread to Sydney's CBD this afternoon, beginning outside the United States Consulate and spreading through the city's streets to Hyde Park.
The ABC understands the protest was sparked by a mass text message saying: "We must defend the honour of our prophet, we must act now."
Follow our live blog for developments as they happen:
6:28pm: In related news in the United States, a California man has been escorted to an interview with federal officers probing possible probation violations stemming from the making of the anti-Islam video that triggered violent protests in cities across the world.
A Los Angeles County Sheriff's spokesman said Nakoula Basseley Nakoula - linked to the film's production - voluntarily left his home, accompanied by sheriff's deputies, to meet with the officers in the Cerritos Sheriff's Station.
"He will be interviewed by federal probation officers," sheriff's spokesman Steve Whitmore said.
"He was never put in handcuffs... It was all voluntary."
But he said Mr Nakoula was not in custody.
6:20pm: Here is more of what NSW Police Superintendent Mark Walton told reporters in Sydney a short time ago:
6:15pm: New South Wales Police Minister Mike Gallagher has just spoken to ABC News 24 . Here is some of what he had to say:
6:00pm: Police have defended their response to demonstrations in Sydney, part of a Muslim protest against a controversial film about the Prophet Mohammed.
In a press conference, Superintendent Mark Walton said eight people were arrested during the "unannounced protest".
Up to 150 police officers attended the incident throughout the day. Six officers were injured, including two who were taken to hospital for treatment.
Two police vehicles were also damaged.
Superintendent Walton said the protesters have now "self-dispersed" throughout the city. Police remain at the scene.
5:50pm: Sydney police are holding a press conference. A spokesman said up to 150 officers attended the protest and six officers were injured. Two have been treated in hospital. Watch live here.
5.41pm: Here's a photo Josh Bavas took of the moment the protest turned violent:
5.15pm: Reporter Josh Bavas has been live-tweeting from the scene.
Muslims have been tweeting him to try and spread the word that not all agree with the actions of the protesters.
"Josh, Please talk about this in your live crosses. Many Muslims are condemning violent actions of those protestors," tweeted @MariamVeiszadeh.
"Those people do not represent me! The violence is far more insulting then the movie itself."
5.12pm: Reporter Josh Bavas has talked to ABC News 24 about the moment the protest turned violent.
"Some people in their cars ... were trapped while the protesters were running past, with police quite close behind them," he said.
"Because the protest spread out so quickly... police were scrambling to get together.
"I heard one man yell out 'shame on you' before the protesters [turned on him]. I don't know if he was injured."
5.10pm: Journalist Jamila Rizvi was shopping at the scene earlier today. She has told ABC News 24 it was much calmer earlier on.
She says the women and children who were present earlier have now gone, and believes a small minority has taken over the protest.
She says it would be a shame if there was a backlash against the Muslim community in the wake of today's protest.
5.00pm: Are you wondering about the film which triggered the protests? Here's some facts:
4.45pm: The Hyde Park protest has taken a violent turn as police scrambled to control angry demonstrators.
Several people were reportedly injured as protesters pulled down barricades and shocked passers-by took cover.
Reporter Josh Bavas has tweeted: "Scenes very ugly. All over streets."
He says police are scrambling towards Oxford Street from Hyde Park.
4.30pm: Before the violence erupted, the ABC's Winsome Denyer told ABC News 24 the situation appeared to be cooling:
4.20pm:The group is made up of Muslim men, women and children of all ages.
One protester was carrying a placard that read "behead those who insult the Prophet".
The group shouted "down, down USA", while another protester yelled: "Our dead are in paradise. Your dead are in hell."
Here, the ABC talks to some of the demonstrators about why they are there:
Earlier in the afternoon, ABC reporter Josh Bavas described heated scenes in Hyde Park.
Bavas says the protest is linked to a controversial low-budget film, Innocence of Muslims, which denigrates the Islamic Prophet Mohammed and belittles the religion he founded.
The film touches on themes such as paedophilia and homosexuality, while also showing the Prophet sleeping with women, talking about killing children and referring to a donkey as "the first Muslim animal".
"We are sick and tired of everyone mocking our beloved Prophet," protester Houda Dib told AFP.
"They have no right to mock our Prophet. We don't go around mocking anyone's religion."
One speaker called for calm, saying the aim of their protest had been to send a message.
"We are here for the sake of our God," he said.
"The message is clear, you cannot mock (the Prophet)."
ABC reporter Emma Pollard was caught in the earlier Martin Place protest and says police tried to form a line in front of the demonstrators.
She says police used pepper spray on protesters, who were throwing objects and bottles of water at the officers.
"I saw one police officer get dragged out into a clear area and he had lots of blood all over his face," she said.
"I could feel the pepper spray catching in the back of my throat so it was drifting everywhere."
The Ambulance service says paramedics have treated at least one person with head injuries.
The Sydney protests follow a furious wave of anti-American violence across the Middle East and North Africa.
A crowd invaded the US embassy compound in Tunisia, and guards at the US embassy in Khartoum, Sudan, fired warning shots at protesters.
Fresh violence erupted in Yemen and Cairo and demonstrations took place in Bangladesh, Indonesia, Malaysia, Pakistan, Iraq, Israel and the Gaza Strip, Morocco, Syria, Kuwait, Nigeria and Kenya.
At least six protesters died on Friday alone, and Washington deployed US Marines to protect its embassies in Libya and Yemen.