Hackers from North Korea are reported to have stolen a large cache of military documents from South Korea, including a plan to assassinate North Korea’s leader Kim Jong-un.
Rhee Cheol-hee, a South Korean lawmaker, said the information was from his country’s defence ministry.
The compromised documents include wartime contingency plans drawn up by the US and South Korea.
They also include reports to the allies’ senior commanders.
The South Korean defence ministry has so far refused to comment about the allegation.
Plans for the South’s special forces were reportedly accessed, along with information on significant power plants and military facilities in the South.
Mr Rhee belongs to South Korea’s ruling party, and sits on its parliament’s defence committee. He said some 235 gigabytes of military documents had been stolen from the Defence Integrated Data Centre, and that 80% of them have yet to be identified.
The hack took place in September last year. In May, South Korea said a large amount of data had been stolen and that North Korea may have instigated the cyber attack – but gave no details of what was taken.
North Korea denied the claim.
South Korea’s Yonhap news agency reports that Seoul has been subject to a barrage of cyber attacks by its communist neighbour in recent years, with many targeting government websites and facilities.
The isolated state is believed to have specially-trained hackers based overseas, including in China.