A heavily armed border crossing between North and South Korea that allows the North access to $2 billion in trade a year, one of its few avenues to foreign currency, remained open on Thursday, March 28 despite Pyongyang's move to cut communications, Reuters reported.

North Korea on Wednesday severed the last of three telephone hotlines with South Korea as it readied its troops to face what it believes to be "hostile" action from Seoul and Washington. The phone line is used to regulate access to the Kaesong industrial park on the North Korean side of the border as well as for military communications with the South.

Nearly 200 South Koreans and 166 vehicles carrying oil and materials drove into the park just inside the North early on Thursday after North Korean authorities used a separate phone line from the park's management office to allow access, South Korean officials said.

The North has already cut a direct hotline to U.S. military forces stationed in South Korea and a Red Cross line that had been used by the governments on both sides.

Severing hotlines is one of the least threatening but symbolic things Pyongyang can do to raise tensions and at the same time pressure Seoul and Washington to restart dialogue, said Yang Moo-jin of the University of North Korean Studies in Seoul.

North Korea periodically cuts the lines. Its latest moves follow UN sanctions imposed for its February 12 nuclear test and routine drills by South Korean and U.S. forces. Pyongyang has also scrapped an armistice that ended the 1950-53 Korean War.