North Korean hackers have reportedly stolen a large cache of military documents from South Korea, including a South Korean-U.S. plan to “decapitate” North Korea’s leader Kim Jong-un.

Rhee Cheol-hee, a member of South Korea’s ruling Democratic Party who serves on the defense committee of the National Assembly, said hackers had stolen the top secret plans from the country’s defence ministry database.

The full extent of the hack is still not know, as around 80 per cent of the contents of the 235 gigabytes of leaked data is yet to be identified, Mr Rhee said.

The cyber attack occurred 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 hack – but no further details were given.

North Korea immediately denied the claim and also accused South Korea of “fabricating” the claims.

South Korea’s ruling Democratic Party is led by President Moon Jae-in. Mr Jae-in came to power in the May election after the impeachment of Park Geun-hye, who was the leader of the Saenuri Party. The reported hacking took place while she was president of South Korea.

News that North Korea is likely to have accessed the Seoul-Washington plans for all-out war in the Koreas will do nothing to soothe tensions between North Korea and the US.

The two nations have been at verbal loggerheads over the North Koreas nuclear plan, with Donald Trump pressing for a halt to missile tests and Kim Jong-Un vowing to continue them.