Chinese fighter-plane hangars revealed in disturbing new satellite images of the South China Sea would allow Beijing to rapidly shift military hardware on to artificial islands to control the key waterways, Australia's former national security adviser says.

The remarks by Andrew Shearer, who served as Tony Abbott's national security adviser, came amid rising concern among military experts that China could declare a so-called "air defence identification zone" (ADIZ) in the South China Sea, requiring foreign military aircraft to ask permission before flying through.

The presence of about 70 hangar spaces for strike fighter aircraft indicates Beijing is at least giving itself the option of declaring a zone, dramatically raising the stakes with countries including Australia. The stationing of fighters could be used to enforce the zone.

The RAAF routinely flies patrols over the South China Sea, meaning its planes would need to challenge China were any zone declared.