North Korea ready to "pre-emptively attack and liberate Seoul"
Kim's rhetoric has grown increasingly provocative as USA and South Korean troops conduct large-scale military exercises and following the imposition of tough new United Nations sanctions against Pyongyang.
The National Intelligence Service told a parliamentary committee meeting that the North unsuccessfully tried to hack into the railway control system and computer networks of financial institutions in South Korea, according to the office of lawmaker Joo Ho-young who attended the private meeting.
But the North has been particularly irked by the start of the weeks-long joint military exercises in the South last Monday. Pyongyang has denied the allegations.
The reports emerged as Pyongyang threatened retaliation against US and South Korean forces taking part in annual joint military drills. On Friday, leader Kim Jong-un also called for bolstering nuclear capabilities with more tests.
North Korea has said it is developing submarine-launched ballistic missiles although doubts about that were raised after Western experts said publicly released footage of tests appeared to be fake. Tensions have heightened on the Korean Peninsula recently.
Pyongyang's rhetoric has become steadily more aggressive since the United Nations imposed strengthened sanctions against the reclusive state for its nuclear test and long-range rocket launch in January and February, respectively.
Seoul's new nuclear envoy, Kim Hong-kyun, issued the warning after holding talks with his US counterpart, Amb.
A North Korean submarine operating off North Korea's east coast has gone missing.
The projects involved are the Mount Kumgang tourism resort, and the Kaesong joint industrial complex.
Even after the war, the U.S has kept thousands of troops in South Korea, according to the U.S. Forces Korea webpage "to deter aggression and if necessary, defend the Republic of Korea to maintain stability in Northeast Asia" . The North has denounced the exercises as "nuclear war moves" and threatened to respond with an all-out offensive.
The KCNA reported that Kim underscored the need to further develop nuclear weapons in order to prepare "to make nuclear strikes at the enemies from anywhere on the ground, in the air, at sea and underwater". The North has conducted a number of what is says were successful tests of a submarine launched ballistic missile.