The venue of G-20 summit here has been caged with metal barricades to prevent over 10,000 protesters, expected to take part in a anti-G-20 rally this weekend, from causing any disruption.
Police on Wednesday night installed the barriers - a series of metal cages about two-square-metres and more than a metre high - on roads around the Grand Hyatt hotel and diverted the traffic onto alternative routes, local media reported on Thursday.
A police spokeswoman said the barriers were designed to separate police and protesters and it was the first time they had been used in Australia.
These arrangements were being made in wake of a secret conference of an underground network of activists in Melbourne yesterday who are plotting a series of interruptions to this weekend's summit, she said.
Australian Treasurer Peter Costello who is chairing the summit has asked protesters to not to turn to violence.
The police is also keeping a watch on a breakaway activist group called 'A Space outside' which has urged direct confrontation and labelled the mainstream campaign ineffectual.
The G-20 meeting will be attended by Finance Ministers and Central Bank governors from 19 countries besides the European Union.