North Korea blocks South workers from Kaesong zone
3 April 2013 Last updated at 13:41 BST
North Korea has stopped South Koreans from crossing the border to work at the jointly run Kaesong industrial zone, for the first time since 2009.
Seoul said about 800 South Koreans who had stayed overnight at the complex were being allowed to return.
Kaesong is a crucial revenue source for the North, which has not indicated how long the entry ban will last.
Lucy Williamson reports from Seoul.