Concerns about North Korean terror attacks are mounting after a South Korean thinktank warned Pyongyang has amassed an arsenal of 1,000 drones.
The Korea Institute for National Unification, a state-run organisation in South Korea, claims the country could use the drones to conduct far-away terrorist attacks with chemical and biological weapons.
It also claims the country is focused on building up this arsenal to compensate for the inferiority of its airforces compared to its southern neighbour.
Previously it was reported that North Korea was developing a drone called the Bangyhun-5, capable of spreading radioactivity over a vast area.
Kim Hyeung-kwang, head of North Korea's Intellectuals Solidarity, a dissident collective resident in South Korea, said in December that "North Korea began to develop a large drone for reconnaissance and attack purposes in 2012 after its current leader Kim Jong-un took power from his late father Kim Jong-il."
Addressing a press conference in Seoul, he added "the latest drone is 'Banghyun-5' which was produced at a local airplane repair plant."
North Korea-focused news site Yonhap reports that the Banghyun 5 is a stealth drone, comprising carbon and titanium. It reportedly possesses a 900-litre fuel tank, weighs 1.5 tonnes and can fly up to 10 hours at a speed of 200 kilometres per hour.
Pyongyang is thought to possess around 25 chemical agents, including six nerve agents, as well as 13 types of pathogens including anthrax.
The country has refused to sign up to the Chemical Weapons Convention, although it did sign up to the Biological Weapons Convention in 1987.