Angry members of the Muslim community tipped off police that radical Islamists were sending around inflammatory text messages garnering support for Saturday's protest over a video mocking the prophet Muhammad.
Six men were arrested following clashes in which two police officers and 17 others were injured as protesters targeted the US consulate in Martin Place, before rolling clashes throughout the CBD with heavily armed police began.
Police Commissioner Andrew Scipione said this morning that members of the specially formed Strike Force McAllister were making quick progress in hunting down those responsible for spreading the message, which urged people to join the protest because "we must act now" to "defend [the prophet's] honour".
Mr Scipione said that, while police had been unaware of the planned time for the demonstration, they were on notice that something was set to occur, courtesy of the messages being forwarded.
"Many of them were sent to us by people within the community who were outraged by what they were receiving on their SMS system or on their Facebook page and so they brought them to our attention," Mr Scipione said at a press conference this morning.
And he said officers would similarly be on standby and ready to respond to any further protests by extremist Muslim groups this weekend.
Suggestions have already been made that the same individuals who clashed with police on Saturday were planning to protest again this weekend.
However, Mr Scipione urged them to organise it lawfully and with police co-operation.
"You can be assured that we will have all of the resources that we need in the right place at the right time for whatever might eventuate," he said.
He disputed claims that police were caught by surprise, saying they had "some intelligence that was made available" and there were almost 200 police in the city. He said there was not much more police could have done to prevent a small number of people from turning violent.
Police Minister Michael Gallacher said a male protester caught on camera smashing a police car with a milk crate would be "coming to a police station near him very shortly".
"I was disgusted with what I saw," Mr Gallacher said.
The ambassador to the United States, Jeffrey Bleich, thanked police for protecting the embassy on Saturday and said it was "business as usual" today.
He would not say if security had been beefed up for him or his staff in the wake of the international violence, sparked by the online video.
"I was particularly heartened by the overwhelming outpouring of support that came for America in the aftermath," he said.
Keysar Trad, founder of the Islamic Friendship Association of Australia, said the language used by some protesters during the riots was very concerning.
"We're always on the lookout for people who use inflammatory terms and, when we find them, someone will go and talk to them and explain to them that this is the wrong way to preach," he said.
"It becomes a challenge for the community to put things into perspective."