The United States has warned its citizens to keep away from Sydney's Martin Place and Hyde Park this weekend amid fears of another outbreak of violence.
A letter titled "Emergency Message for US Citizens" sent to all those registered with the US consulate says that "law enforcement authorities" have advised that anti-American demonstrations are possible on both Saturday and Sunday.
It also warns Melbourne residents to avoid protest areas planned in this city this weekend.
"Should they occur, US citizens should avoid the immediate demonstration areas," the letter reads.
"Fast-forming anti-American protests in Australia remain possible."
A spokeswoman for the US consulate told Fairfax Media that the last time such a warning was issued to its citizens was for the Queensland floods in early 2011.
The letter also urges Americans to avoid attracting attention to themselves as US citizens.
"The Department of State remains concerned about the threat of violence against US citizens and interests throughout the world. US citizens are reminded to maintain a high level of vigilance, to be aware of their surroundings and to take appropriate steps to increase their security awareness," it reads.
Meanwhile Muslim leaders have thrown their support behind the NSW Police ahead of the rumoured protests this weekend.
The grand mufti of Australia, Dr Ibrahim Abu Mohamed, who has never fronted the media in such a way, joined two prominent sheikhs, riot police and the NSW Police Deputy Commissioner, Nick Kaldas, this afternoon to declare their support for the actions of police during and after the violent protests last weekend.
The announcement is likely to anger some members of the Muslim community who have insisted that police baited protesters in Sydney's Hyde Park and responded heavy-handedly.
Some have expressed outrage that their leaders have "sided" with the police.
"We are all on the same side," said Dr Mohamed, through his translator.
"This country is not great or famous for its koalas and kangaroos. It is great for its freedom."
Mr Kaldas said the police had no intelligence to suggest more protests would be held this weekend. However, Fairfax Media has seen messages circulating on Facebook urging people to demonstrate again. One message posted by a woman has attracted hundreds of comments. It says: "This Sunday 23 September 1 pm at Hyde Park we can all bring own pepper spray !"
Mr Kaldas said riot police would be on standby tonight for a pro-Palestinian protest in Parramatta that had been planned weeks in advance and was authorised by police.
There will also be a police presence in the city on the weekend.
Muslim leaders called for calm and said violent protests were against the teachings of Islam.
Asked what should happen to anyone who protests again, Sheikh Kamal Mousselmani from the Supreme Islamic Shia Council of Australia said: "I would be telling the police to arrest them all."
There are fears that anti-Islamic cartoons published by a French magazine overnight could inflame tensions in Australia. Mr Kaldas said that the cartoons were "probably not helpful" but should not be used as an excuse for criminality.
He said police would be visible at Friday prayers around the city; the first prayer gatherings since the violent protests last Saturday.