The recent discovery of three drones, presumably from North Korea, is drawing keen attention to the types of unmanned aerial vehicles the communist state has and their military capabilities.

Pyongyang is known to have begun developing military drones in the 1990s as they could serve as a lethal yet low-cost weapons system.

Seoul officials believe that the North has imported a series of drones, which were made in China, Russia and other nations, and modified them to serve for its specific military objectives. They say the North has already deployed weaponized drones to some of its frontline units.