Federal Greens MP Adam Bandt has accused Immigration Minister Peter Dutton of being a "terrorist" over the treatment of 600 asylum seekers at the now-closed Manus Island detention centre.
"What is happening between Canberra and Manus has ceased to be government and has become terror," Mr Bandt told a rally in Melbourne's CBD attended by hundreds of people on Saturday.
"If the definition of terror is to use violence and threaten people's lives for political purposes, then Peter Dutton is a terrorist."
More than 600 refugees have barricaded themselves in the mothballed detention centre, which closed on Tuesday.
Food and drinking water has run out and the group is too scared to move to alternative accommodation in the main township out of fear they will be attacked by locals.
Mr Bandt says the immigration minister must be held to account for what's happening on Manus.
"To look at the face of Peter Dutton is to stare into the cold eyes of someone who is prepared to kill someone for political gain," he said.
Two men who remain inside the closed detention centre have pleaded with Australians to help them.
"We are forgotten people who have been tortured ... even though we have committed no crime," one man said in a recorded message played at the rally.
"Our situation is getting worse and we need your help," the other man said.
"Will Australians stand up and speak for humanity if you think refugees are humans?"
Legal worker Sophie L'Estrange told the rally she was working on the island during the Good Friday shooting earlier this year.
She said for 45 minutes she heard what she believed were the sounds of people dying.
The protest, organised by the Refugee Action Collective of Victoria, began outside Victoria's' State Library in Swanson Street and was followed by a march to Flinders Street.
