The North also threatened to shut down an industrial zone it operates jointly with the South near the heavily armed border between the two sides if Seoul continued to say the complex was being kept running for money.
The two Koreas have been technically in a state of war for six decades under a truce that ended their 1950-53 conflict. Despite its threats, few people see any indication Pyongyang will risk a near-certain defeat by re-starting full-scale war.
“From this time on, the North-South relations will be entering the state of war and all issues raised between the North and the South will be handled accordingly,” a statement carried by the North’s official KCNA news agency said.
KCNA said the statement was issued jointly by the North’s government, ruling party and other organizations.
There was no sign of unusual activity in the North’s military to suggest an imminent aggression, a South Korean defense ministry official said.
The North has been threatening to attack the South and U.S. military bases almost on a daily basis since the beginning of March, when U.S. and South Korean militaries started routine drills that have been conducted for decades without incident.
Many in the South have regarded the North’s willingness to keep open the Kaesong industrial zone, located just a few miles (km) north of the border, as a sign that Pyongyang will not risk losing a lucrative source of foreign currency by mounting a real act of aggression.
The Kaesong zone is a vital source of hard currency for the impoverished state and hundreds of South Korean workers and vehicles enter daily after crossing the armed border.
“If the puppet traitor group continues to mention the Kaesong industrial zone is being kept operating and damages our dignity, it will be mercilessly shut off and shut down,” KCNA quoted an agency that operates Kaesong as saying in a statement.
The threat to shut it down could sharply escalate tensions because it would suspend a symbolic joint project run by the rivals. It could also trap hundreds of South Korean workers and managers of the 123 firms that have factories there.