An autonomous robot that can administer a lethal injection is set to be the latest weapon in the fight against the invasive crown-of-thorns starfish on the Great Barrier Reef.

The starfish preys on coral and is responsible for destroying up to 40 per cent of the reef.

Researchers from QUT are close to finishing trials on a robot which will be primed to find and kill the starfish.

The mechanical hitman, known as COTSbot, uses GPS and a series of thrusters to cruise within one metre of the seafloor.