"I don't think this will lead to an immediate shutdown of the Kaesong industrial complex" said Kim Yong-hyun, a North Korea expert at Seoul's Dongguk University.

WSJ: Seoul to Pull Workers out of North Korea

Defense officials reported no signs of cyberattacks on its ministry's computer network and had no immediate details about the broader shutdown.

WSJ: South Korea Banks, Media Report Possible Cyberattack