Two dummy security cameras found inside the G20 security zone in Brisbane lay undiscovered for at least three days.
The cameras were reportedly designed to project anti-G20 slogans during the summit.
In the first security breach of the summit, the devices were found in South Brisbane, although their exact location wasn't revealed.
"They are described as having the capability to project images and do not present any community safety concerns," a police spokeswoman said on Tuesday.
Areas of South Brisbane will become the focus of a complex security operation in coming days when G20 events are held at the Brisbane Convention and Exhibition Centre (BCEC).
The devices were installed before security was ramped up and were found after more officers were on the beat, police said.
Under the G20 legislation, a central declared security area came into effect in Brisbane from November 8, however, a tougher restricted area around the BCEC was activated earlier, on November 1.
The devices were installed some time before November 8, police believe.
