The protest was held ahead of Saturday’s G20 summit in Brisbane. The leaders are expected to discuss the Ebola crisis, the campaign against Islamic State militants and the struggling world economy, with a new two percent growth target on the table.
Australia is mounting the biggest peace-time deployment of police and soldiers, bracing themselves for everything from protests to mass hostage-taking.
Bomb-detecting robots will be on hand, along with a drone for crowd surveillance.
The operation involving 6,000 police and 1,900 troops will be a high-visibility balancing act between protecting the world’s most powerful leaders at a time of heightened terrorism fears and showcasing what Australia hopes will be seen as its tolerance for political dissent.