Security breach ahead of G20 summit

A plot to convey anti-G20 messages using fake CCTV cameras in Brisbane's restricted zone has been discovered, in a significant security breach days before the world's most powerful leaders arrive.

A number of devices designed to look like CCTV cameras were found around the Brisbane convention centre where world leaders, including US President Barack Obama and Russian President Vladimir Putin, will converge this weekend.

The development came as the advance team for Mr Putin touched down and as Brisbane's ring of security was tightened.

The fake cameras were found in an area declared a no-go zone for anyone who doesn't have security clearance, and despite years of planning for the event.

"Two devices have been found in the South Brisbane area in the past few days," a spokeswoman for Queensland Police said.

The devices were designed to project images onto flat surfaces and would have been able to be triggered remotely.

It's believed the cameras were installed prior to the commencement of the G20 Safety and Security Act, which came into force on November 8.

They were found since police ramped up their patrols in the restricted zone.

Police refused to say how long the devices may have been in place.

"They are described as having the capability to project images and do not present any community safety concerns," police said.

The security breach comes as authorities prepare for dozens of protests over the coming days, targeting a range of issues from climate change to indigenous rights, and the possibility of violent anti-capitalism demonstrations.

Activist group Anonymous has urged people to don masks and rally at the leaders' summit on Saturday morning, in defiance of a police ban on face coverings.

"Calling all anons far and wide to mask up and march on the Brisbane Convention Centre," an online post said.

Despite issues around road closures and safety, Queensland Premier Campbell Newman has again said people should feel free to head into the CBD while the conference is on.

He scoffed at a warning by Katter Party MP Ray Hopper, who's urged his constituents to stay away from the city due to the possibility of "very great personal danger".

"I think that's a bit over the top," the premier said.

A Russian cargo plane loaded with vehicles and hardware arrived on Tuesday at a special G20 terminal set up at Brisbane's international airport.

Mr Putin will arrive later in the week, as tensions remain over the MH17 disaster, in which 298 people died, including 38 Australians.

The world's premier economic gathering will involve 25 leaders from some of the biggest and emerging economies, with a chief mission of boosting global growth by two per cent above current projections.

Also high on the agenda are plans to establish a global infrastructure hub, as well as negotiations on a crack down on tax havens.