The announcement by the Committee for the Peaceful Reunification of Korea followed Seoul's decision on Wednesday to shut down Kaesong operations as punishment for the North's recent nuclear test and long-range rocket launch.
In a statement published by the official KCNA news agency, the committee said it was closing Kaesong and declaring it a military area.
It also announced the cutting of all military communications with South Korea, including the main channel through the border truce village of Panmunjom.
It did not specify how long the links would be cut for. "South Korean enemy forces will experience themselves the harsh and painful price they should pay for halting the Kaesong industrial complex," it said.
All South Koreans were ordered to leave Kaesong by 5:00pm Pyongyang time (0830 GMT) and told they could take nothing but their personal possessions.
"We seize all assets of the South Korean companies and related organisations including machinery, raw materials and goods," the statement said.
- AFP