North Korea on Thursday demanded a four-fold increase in salaries at a trade zone where South Koreans run factories, threatening to kill off the last credible interaction between Seoul and Pyongyang.

North Korea’s moves against the Kaesong industrial complex come hard on the heels of a draft UN resolution to pursue tough new sanctions against the communist state. Pyongyang infuriated the UN Security Council by detonating an atomic bomb last month and blasting a long-range missile over Japan in April.