North Korea has been accused of hacking and stealing secret blueprints of South Korean warships and submarines. Hackers reportedly hit Daewoo Shipbuilding and Marine Engineering Co last year and stole around 40,000 documents, including classified military records as well as information on weapons and construction technology.

South Korea's Aegis-equipped submarines and ships, several of which have been built by Daewoo, are considered vital for the country's defence in view of constant North Korean threats.

South Korean lawmaker Kyeong Dae-soo was cited by the Dong-A Ilbo newspaper as saying that the breach was discovered by the South Korean defence ministry. The stolen data includes around 60 classified military documents, the South China Morning Post reported.

"We are almost 100% certain that North Korean hackers were behind the hacking and stole the company's sensitive documents," Kyung Dae-soo of the main opposition Liberty Korea Party, told Reuters. According to Kyung, the team investigating the hack concluded that North Korea was behind the attack after they reportedly uncovered similarities with other attacks known to have been previously conducted by North Korean hackers.

A spokesperson for Daewoo Shipbuilding said the firm was in the process of confirming details of the remarks made by Kyung.

Earlier in the month, North Korea was accused of hacking and stealing a massive trove of military secrets from South Korea, including Washington-Seoul wartime operation plans intended to "decapitate" Kim Jong-un's dictatorial regime.

Last week, British authorities also accused North Korea of orchestrating the historic WannaCry ransomware epidemic that swept across the globe earlier in the year. Pyongyang has denied the accusations.

Earlier in the month, notorious North Korean hacker group Lazarus was suspected of being behind a massive cyberheist in Taiwan that saw millions stolen. The hacker group is widely considered to be Pyongyang's tool to generate money for the impoverished country.