North Korea says it is cutting off all military communication with South Korea, warning that war "may break out at any moment."
On March 27, Pyongyang cut a hotline that helps coordinate travel by South Korean workers to a North Korean industrial complex.
North Korea recently shut off a Red Cross hotline and one with the U.S.-led UN command on the North-South border.
Also on March 27, North Korea warned South Korean President Park Geun-hye to "behave with discretion" to avoid a "horrible disaster."
Pyongyang announced on March 26 that its rockets are now targeting U.S. bases in Guam, Hawaii, and the U.S. mainland.
The U.S. Defense Department said it is ready for "any contingency."
The United States and South Korea are conducting joint military exercises until the end of April.
Based on reporting by Reuters and the BBC