North Korea has followed through on promises to severely restrict crossings of its border with South Korea.  The North has curtailed travel to joint North-South cooperation zones and reduced South Korean staffing there to skeleton levels. VOA's Kurt Achin has more from Seoul.

South Korean Unification Minister Kim Ha-Joong (File)

South Korean Unification Minister Kim Ha-joong said Monday North Korea's restriction of the North-South border "cannot be justified, and must be repealed immediately."

As they had threatened to do for weeks, Pyongyang officials announced sharp new restrictions, Monday, about who can cross its southern border and when.  The North says it will allow vehicles to enter from the South only six times a day, down from a usual 19 openings a day.

Out of more than four-thousand South Korean managers and officials who supervised a cooperative industrial park in the North Korean city, Kaesong, only 880 South Koreans have permission to remain. 

Unification Ministry Spokesman Kim Ho-nyeon expressed South Korea's "deep regret" at the restrictions, which he says violate North-South agreements.

He says the border restrictions impede production and decrease market confidence.

Monday's steps are part of a gradual process North Korea warns may lead to the complete severing of ties between the two Korea's, which never formally ended their 1950's war with a treaty.

Last week, North Korea ended a tour of Kaesong and halted daily freight-train crossings from the South. A  tourism zone at the North's Mount Kumgang remains closed, after the July shooting death of a South Korean housewife by North Korean soldiers.

The Kaesong industrial park and the Kumgang tourism zone were the centerpieces of a ten-year South Korean policy that sought to engage North Korea by showing it was willing to send billions of dollars in aid and investment, while asking little in return.

However, that generosity failed to stop the North from testing a nuclear weapon, two years ago -- an event that fueled last year's election of conservative South Korean President Lee Myung-bak.  Mr. Lee has said aid and investment needs to be more in line with Pyongyang's cooperation on the nuclear and other issues.

North Korea calls President Lee a "traitor," and warned last month it would turn the South into "debris" if he did not honor agreements to spend billions building infrastructure for the impoverished North.   Pyongyang has also warned South Korea to stop private groups from launching leaflets, by balloon, into the North.