Peculiar bubbles investigated in G20 zone

Queensland water police are investigating the cause of peculiar bubbles in the Brisbane River within the declared G20 zone.

Divers and police boats were at the scene near the Queensland Performing Arts Centre at South Bank on Friday afternoon.

"Water police are checking to see what the source of the bubbles are, but it's not believed to be suspicious at this stage," a police spokesman told AAP.

The investigation has proved popular on social media, with many users joking the bubbles could be emanating from a Russian submarine.

Large parts of Brisbane CBD are deserted on the eve of the G20 leaders' summit, except for scores of police who can be seen patrolling the area.