Hundreds of people in Brisbane, Sydney and Melbourne have protested in support of the WikiLeaks website and its founder Julian Assange.
More than 500 people rallied outside Sydney's Town Hall, while about 350 people gathered outside the Brisbane office of the Department of Foreign Affairs and Trade.
In Sydney, Greens Senator-elect Lee Rhiannon criticised the government's response to the 250,000 documents leaked by Wikileaks in recent weeks.
"Julian Assange is an Australian. That makes me and I'm sure it makes you feel very proud," Ms Rhiannon told the crowd.
"But we can certainly not feel proud of our government."
Prime Minister Julia Gillard insists the actions of Mr Assange, an Australian citizen, and his WikiLeaks website are illegal.
But the federal government is leaving it to the Australian Federal Police to determine whether Mr Assange has broken any Australian laws.
Simon Skew, Pirate Party spokesman, said whistleblowers were essential to democracy.
"Public disclosure is in the public interest and it's completely legitimate," he told the heavily-policed protest on Friday.
"We have a right to know about our government's operations and the circumstances and behind their decisions and policies."
Protesters at the rally, which coincided with International Human Rights day, were vocal about their support for Mr Assange.
"As an Australian citizen. He's got the right to be defended against people calling for his assassination," one protester told AAP.
He's got the right to a fair trial and due process and if he doesn't get that then human rights are certainly being violated."
Supporters repeatedly yelled "shame" and "I am Julian Assange" during speeches by several people.
Earlier in the day, NSW Greens MP David Shoebridge said WikiLeaks had increased transparency and should be applauded for "opening the door on the inner workings of government".
"There are few rights more important than freedom of information," he said.
"Without transparency and freedom of information, decisions occur behind closed doors without any accountability."
In Brisbane, Lawyer Peter Russo, who defended Indian doctor Mahomed Haneef against failed terrorism charges told the rally it was important to understand that the real issue at stake in the WikiLeaks affair is freedom.
"It's not only the freedom of the individual it's the freedom of all of us," he said.
Mr Russo said it was a "fallacy" for governments to believe they had to keep secrets from their people in order to govern, and called for due legal process for Assange.
The Ann Street rally was larger than another held in the city on Thursday night, which drew about 250 people.
Friday's rally was read messages from London-based Australian journalist John Pilger and US dissident academic Noam Chomsky.
Mr Pilger described the defence of Mr Assange and WikiLeaks "one of the most important issues of my lifetime".
He said the issue pitted the military power of the US against the power of public opinion.
"If the Australian prime minister doesn't understand this, we Australians need to remind her that she may head a mercenary government but we are not a mercenary people," Mr Pilger said.
Professor Chomsky, a long-term critic of US foreign policy, said Mr Assange is performing a civic duty.
"Systems of power wish to protect themselves from citizens, while at the same time sparing no effort to intrude into private lives so as to better establish their control," he said.
A significant police presence escorted the chanting marchers, many linked to socialist groups, through the CBD as lunchtime workers and bemused shoppers gave them a generally warm reception.
"Assange is a hero of our time, telling truth is not a crime," the marchers chanted.
Placards praised Mr Assange as Australia's best journalist and urged senior reporters Kerry O'Brien and Laurie Oakes to surrender to him the Walkley awards for journalism they received on Thursday night.
In Melbourne, prominent criminal lawyer Rob Stary has described the Australian government as "sycophants" to the US.
Mr Stary told the rally of hundreds of people outside the Victorian state library that the treatment of Mr Assange was proof of the "subservience of the government in bowing to the US".
Mr Stary compared Mr Assange to fellow Australians David Hicks and Jack Thomas, saying the latter pair's conviction on terrorism charges was helped by the government's "propaganda machine".
The crowd chanted "shame" and cheered another lawyer and Greens politician Brian Walters SC, who urged the government to uphold the "rule of law" and "freedom of speech".
Prime Minister Julia Gillard has said Mr Assange's actions on his WikiLeaks website are illegal.
WikiLeaks boss Julian Assange is currently in a British jail as Sweden seeks his extradition on rape charges.