North Korea said Saturday it has entered a "state of war" with Seoul and threatened to close a jointly run industrial park after US stealth bombers conducted exercises in South Korea, dpa reports.
"From this moment on, the North-South relations will be entering a state of war. All issues raised between the North and the South will be handled accordingly," Pyongyang said in a statement broadcast by the official Korean Central News Agency (KCNA).
The two Koreas have technically remained at war after a ceasefire - signed by the North and the United Nations - ended the 1950-53 Korean War.
The military was awaiting further orders from leader Kim Jong Un, KCNA reported.
Pyongyang's latest threat followed a military rally in the capital Friday, as Kim issued orders to prepare strategic missiles for attack on the United States and South Korea.
Pyongyang was reacting to a show of force by US stealth fighters that flew a 20,000-kilometre round trip to drop dummy bombs onto a South Korean training ground.
A spokesman for the jointly operated Kaesong complex threatened its closure Saturday, according to North Korean state media. Commuters were still being allowed across the border, the Defence Ministry in Seoul said earlier.
Relations have deteriorated since North Korea's third nuclear test on February 12, which led to a strengthening of international sanctions against it.
It has since issued repeated threats, including pre-emptive nuclear attacks.
Russia on Saturday reiterated its call for restraint on the Korean peninsula. Foreign Ministry official Grigory Logvinov said Moscow could not be indifferent to the developments near the country's eastern borders, the Itar-Tass news agency reported.
"We hope all the parties will show maximum responsibility and restraint and nobody will cross over the dangerous line, behind which there will be no return," Logvinov said.
Hundreds of South Koreans travel across the border to the Kaesong complex daily, except Sundays.
The complex, where some 50,000 North Koreans work for some 120 South Korean companies, is one of only sources of foreign currency for impoverished, isolated North Korea.