North Korea says it has entered a "state of war" with South Korea and has warned any provocation by Seoul and Washington will escalate into a nuclear war.
In a statement carried by the North's official KCNA news agency Saturday, Pyongyang said all issues between the two Koreas will be handled according to "wartime regulations."
In response, South Korea's defense ministry urged its northern neighbor to stop making threats. The ministry also said the South's forces will completely punish the North if there is a provocation.
The White House said it takes the latest statement by Pyongyang seriously. National Security Council spokeswoman Caitlin Hayden said the North has a long history of bellicose rhetoric, and that Saturday's threat follows a familiar pattern.
Also Saturday, North Korea threatened to shut down a joint industrial complex with the South. A North Korean spokesman said the Kaesong industrial complex just north of the line separating the two countries will close if Seoul undermines the North's dignity.
After the North declared a "state of war" Saturday, hackers apparently targeted several North Korean web sites and made them temporarily unavailable. Individual hackers told VOA they were responsible for the outages.
North Korea has directed a series of vitriolic comments at the U.S. and South Korea in recent weeks. Pyongyang has threatened to turn Seoul into a "sea of fire" and has warned of firing rockets at U.S. military bases in Guam, Hawaii and Japan.
Analysts say the North is not yet capable of mounting an operational nuclear warhead on a missile. But many of its neighbors are worried they may be easier targets for Pyongyang's conventional weapons.