The move is the latest in a series of threats from North Korea in response to new UN sanctions imposed after its third nuclear test in February and to “hostile” military drills under way joining the US and South Korea.
The North has already stopped responding to calls on the hotline to the US military that supervises the heavily armed demilitarised zone and the Red Cross line that has been used by the governments of both sides.
“Under the situation where a war may break out at any moment, there is no need to keep north-south military communications which were laid between the militaries of both sides,” the North’s KCNA news agency quoted a military spokesman as saying.
“There do not exist any dialogue channel and communications means between the DPRK and the US and between the north and the south.”
Despite the shrill rhetoric, few believe North Korea, formally known as the Democratic People’s Republic of Korea, will risk starting a full-out war.
North and South Korea are still technically at war after their 1950-53 civil conflict ended with an armistice, rather than a treaty, which the North says it has since torn up.
The “dialogue channel” is used on a daily basis to process South Koreans who work in the Kaesong industrial project, where 123 South Korean firms employ more than 50,000 North Koreans to make household goods.
On average, about 120 South Koreans are stationed at Kaesong at any one time.
It is the last remaining project in operation between the two Koreas after the South cut off most aid and trade in response to Pyongyang’s shooting of a South Korean tourist and the sinking of a South Korean naval vessel.
Kaesong is one of North Korea’s few hard currency earners, producing e1.56bn a year in trade with the South, and Pyongyang is unlikely to close it except as a last resort.
The North’s military spokesman representing its “supreme command” did not mention Kaesong, which has suffered temporary shutdowns before.
The South’s government said it would take steps to ensure the safety of the workers at Kaesong.
Other examples of Korean co-operation have come and gone. The recently ended five-year tenure of hard-line South Korean president Lee Myung-bak saw relations plunge.