The first protest is being staged in Sydney today, where US President George W. Bush is due to arrive for a summit of 21 Asia Pacific Economic Co-operation (Apec) leaders.
Chanting anti-Bush slogans, about 100 protesters staged a peaceful but noisy demonstration outside Sydney's main railway station.
The majority of Australians are opposed to the US-led Iraq war, despite their government's full support and Australian troops serving in Iraq.
Police on jet skis patrol Sydney Harbour near the Asia-Pacific Economic Cooperation (APEC) summit venue Photo: Reuters
Ringed and photographed by police, protesters waved anti-Iraq war and anti-Bush posters, while a tall black and white skeleton puppet danced as rush-hour commuters headed home.
Within an hour most protesters, who were outnumbered by police and media, had dispersed.
Australian police said they expect violent protests during the Apec summit week and are undertaking the country's biggest-ever security operation.
Authorities have erected a five-kilometre security fence across the central business district to isolate the leaders in the Sydney Opera House and nearby hotels. A total of 5,000 police and troops are patrolling the city centre.
Protesters plan a major rally on Saturday, the first day the leaders meet, but police have refused to issue a march permit, saying there is intent for violence.
Police took court action today to stop the march. The court adjourned the case until tomorrow, saying protesters had insufficient time to prepare for the case.
With Chinese President Hu Jintao and Russian President Vladimir Putin attending the summit, protesters also plan to demonstrate against human rights abuses in China, nuclear proliferation and global warming.
Sydney school students plan to walk out of classrooms tomorrow to protest against Mr Bush and the Iraq war, but authorities have warned children not to join in any protests. Police warned Sydney residents to avoid protests.
An opinion poll released today found 52 per cent of Australians believed Mr Bush was the worst president in US history. Just 32 per cent said he was not, while the remainder were undecided.