Thursday's notice is the latest unraveling of inter-Korean agreements put in place since a historic 2000 summit to ease tensions and encourage exchanges between the two sides. Yang Moo-jin, a scholar with the University of North Korean Studies in Seoul, says the North is "playing hard ball".

He says North Korea's actions block any exchange of people and resources between the Koreas. He says it is an all-out shutdown.

Regularly scheduled tours of South Korea's side of the heavily armed inter-Korean border were abruptly curtailed Thursday after the North's announcement came out, as a safety precaution.

Professor Yang says the situation could easily escalate.

He says the power struggle taking place between the two Korea's could result in what he says could be "some of the most terrible things to happen since the Korean War".