By Agence France-Presse
Thousands demonstrated in the city against a raft of grievances on the sidelines of an Australia-ASEAN special summit, where Prime Minister Malcolm Turnbull has vowed to tackle human rights issues.
They came together to urge the release of political prisoners in Vietnam, an end to strongman Hun Sen's regime in Cambodia and a halt to the military crackdown on Rohingya in Myanmar.
"We are here to protest issues that are happening in Vietnam, Cambodia, Thailand, the Rohingya -- you name it, we are here to send a clear voice to these governments that you do not mistreat human rights," Vietnamese-Australian protestor Davy Nguyen told AFP.
Leaders from the Association of Southeast Asian Nations including Hun Sen, Myanmar's de facto leader Aung San Suu Kyi and Vietnam's Nguyen Xuan Phuc, are in Sydney for talks. The Philippines' Rodrigo Duterte opted not to attend.
All have been accused of oppression.
"The summit is here, and the (Australian) government needs to do something -- they need to put human rights before economics, before money," Nguyen added.
Among banners was one portraying Aung San Suu Kyi with a Adolf Hitler moustache, calling on her to "Return the Nobel Prize".
The Nobel laureate is accused of failing to do enough to halt the persecution of the Muslim-minority Rohingya community who have been brutally forced out of Rakhine state by the Myanmar military.
Others urged Hun Sen, who is accused of overseeing widespread human rights violations, to quit. The protest followed a rally by several hundred Cambodian-Australians against him on Friday.
"We are here today in solidarity among the communities from Southeast Asia who are facing dictatorship and genocide, of course particularly in the Rohingya community," Shawfikul Islam from the Australian Burmese Rohingya Organisation said.
ASEAN groups Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam, with Australia a dialogue partner since 1974.