Suspected North Korean hackers are believed to have stolen top secret war plans and military documents from South Korea’s Defence Ministry, including a plan to assassinate top leaders of the North, South Korean newspaper The Chosun Ilbo reported on Tuesday.

South Korean lawmaker Rhee Cheol-hee, who is part of the Parliament’s Defence Committee, said about 235 gigabytes of documents were stolen in September 2016 from the Defence Integrated Data Centre. Four-fifths of them have yet to be identified, he said. The Defence Ministry has confirmed the leak.

The stolen documents include contingency plans drawn up in 2015 by the United States and South Korea for the time of war. Plans for South Korea’s special forces as well as information on military facilities and power plants were also accessed, according to the BBC.

North Korea had denied a claim by the South earlier this year that its hackers might have stolen a large amount of data.