Dubbed Unmanned Warrior, the exercise features more than 50 vehicles, sensors and systems on the surface of the sea, underwater and in the air. This is also being held at the same time as Joint Warrior, a UK-led Nato exercise held twice a year, which involves thousands of armed forces personnel.

The exercises are being held in military ranges and sites in Benbecula, Kyle of Lochalsh and off Applecross until 20 October.  Manufacturers of military technology, including BAE Systems, are taking part in the exercise which runs until 20 October.

BAE Systems has described Unmanned Warrior as the world's first large-scale demonstration of "innovative maritime robotic systems".

The Royal Navy has reported that earlier this week nine autonomous systems were operated at the same time, "responding to each other, flying, swimming and diving together, but at different tasks, looking for different things".

The vehicles being used in Unmanned Warrior include BAE Systems' Pacific Class 950 Unmanned Rigid Inflatable Boat. A craft called Maritime Autonomy Surface Testbed (Mast) is also being trialled.