North Korea executed Kim Hyok Chol, its special envoy to the United States, and foreign ministry officials who carried out working-level negotiations for the second U.S.-North Korea summit in February, holding them responsible for its collapse, a South Korean newspaper reported on Friday.

Kim Yong Chol, a senior official who had been U.S. Secretary of State Mike Pompeo’s counterpart in the run-up to the summit between U.S. President Donald Trump and North Korean leader Kim Jong Un in Hanoi, is also said to have been subjected to forced labor and ideological education, the Chosun Ilbo reported.

The North Korean leader is believed to be carrying out a massive purge to divert attention away from internal turmoil and discontent, the newspaper said.