South Korean workers have started shutting down a jointly run industrial park in North Korea. The move Thursday will end, at least temporarily, the Koreas' last major cooperation project as punishment over Pyongyang's recent rocket launch.

It was unclear how long the shutdown at the industrial complex in the border city of Kaesong would last, or even how long the shutdown would take. Pyongyang has yet to comment, but Seoul said that North Korean workers didn't report to work at Kaesong on Thursday.

The shutdown is one of Seoul's strongest available punitive measures and will hurt impoverished North Korea's finances. Seoul said it wants to stop Pyongyang from using hard currency from the park to develop its nuclear and missile programs.