US President Donald Trump walking with North Korea's leader Kim Jong Un during a break in talks at the second US-North Korea summit at the Sofitel Legend Metropole hotel in Hanoi on February 28, 2019.

North Korea executed its nuclear envoy to the United States as part of a purge of officials who steered negotiations for a failed summit between leader Kim Jong Un and U.S. President Donald Trump, a South Korean newspaper said on Friday.

Kim Hyok Chol was executed in March at Mirim Airport in Pyongyang, along with four foreign ministry officials after they were charged with spying for the United States, the Chosun Ilbo reported, citing an unidentified source with knowledge of the situation.

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

The February summit in Vietnam's capital Hanoi, the second between Kim and Trump, failed to reach a deal because of conflicts over U.S. calls for complete denuclearisation of the Korean peninsula and North Korean demands for sanctions relief.

Reuters was unable to independently confirm the report. Previously, North Korean officials have been executed or purged only to reappear with a new title, according to media reports.

A spokeswoman at South Korea's Unification Ministry declined to comment. An official at the presidential Blue House in Seoul said it was inappropriate to comment on an unverified report.

The United States is attempting to check on the reports of the envoy's execution, Secretary of State Mike Pompeo said during his visit to Berlin on Friday

When asked about reports of a "shakeup" of Kim Jong Un's negotiating team in a May 5 interview with ABC News, Pompeo said it did appear that his future counterpart would be somebody else "but we don't know that for sure."

A diplomatic source told Reuters there were signs Kim Hyok Chol and other officials were punished, but there was no evidence they were executed and they may have been sent to a labour camp for re-education.

The newspaper reported that other officials had been punished, but not executed.

Kim Yong Chol, Kim Jong Un's right-hand man and the counterpart to Pompeo before the Hanoi summit, had been sent to a labour and reeducation camp in Jagang Province near the Chinese border, the Chosun Ilbo reported.

Officials who worked with Kim Yong Chol have been out of the public eye since the summit, while seasoned diplomats who appeared to have been sidelined, including vice foreign minister Choe Son Hui, were seen returning to the spotlight.

A South Korean lawmaker told Reuters in April that Kim Yong Chol had been removed from a key party post.