Seoul: North Korea stole blueprints of missile-equipped ships and unspecified submarines in a heist of classified documents from the world's biggest shipbuilder, a South Korean newspaper reported, citing opposition party lawmaker Kyeong Dae-soo.

About 60 classified military documents were among the 40,000 hacked from South Korea's Daewoo Shipbuilding and Marine Engineering Company in April 2016, Dong-A Ilbo said. They included information on construction technology, blueprints, weapons systems, and evaluations of the ships and submarines.

North Koreans dance under a flashcard display of an image of a satellite during the Arirang Mass Games celebrations in Pyongyang last year. Credit:AP

South Korea's Aegis-equipped ships and submarines are key to plans for a pre-emptive strike against North Korea should it send a submarine equipped with ballistic missiles to target key facilities in the South. Mr Kyeong told the newspaper that he received a briefing on the hack from South Korea's Defence Ministry, which inspected the shipbuilder for six months.

Earlier this month, a separate South Korean lawmaker said that North Korean hackers stole military plans developed by the US and South Korea last year that included a highly classified "decapitation strike" against leader Kim Jong-un.