Seoul: North Korea has executed its nuclear envoy to the United States as well as four Foreign Ministry officials who carried out negotiations for the Hanoi summit with US President Donald Trump in February, holding them responsible for its collapse, South Korean reports say.

Kim Hyok-chol was executed at Mirim Airport in Pyongyang, along with four Foreign Ministry executives, in March after they were all charged with spying for the United States, the Chosun Ilbo reported, citing an unidentified North Korean source.

US President Donald Trump talks to Kim Yong-chol, former North Korean military intelligence chief and previously one of leader Kim Jong-un's closest aides, and Secretary of State Mike Pompeo. Kim Yong-chol is said to have been sent to a labour camp. Credit:AP

"He was accused of spying for the United States for poorly reporting on the negotiations without properly grasping US intentions," the source was quoted as saying.

The summit in Hanoi, the second between Kim Jong-un and Trump, failed to reach a deal because of conflicts over US calls for complete denuclearisation of the Korean peninsula and North Korean demands for sanctions relief.