SEOUL (Reuters) - 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, some North Korean officials who were reported to have been executed or purged reappeared later with new titles.

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.

White House spokeswoman Sarah Sanders declined to comment on the reports, saying, “I am not going to comment on intelligence one way or another.”

“I can tell you we are monitoring the situation and continuing to stay focused on our ultimate goal, which is denuclearisation,” she told reporters in Washington.

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.

RISE AND FALL

Kim Hyok Chol was seen as a rising star when he was appointed to spearhead working-level talks with U.S. nuclear envoy Stephen Biegun weeks before the Hanoi summit.

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However, little was known about his expertise or his role in the talks. The four executed alongside him included diplomats working on relations with Vietnam, the Chosun report said.

“This is a man who might provide some tactical advice to the leader but is otherwise a message bearer with little negotiating or policymaking latitude,” said Michael Madden, a North Korea leadership expert at the Washington-based Stimson Centre.

“Instead, they put in someone like Kim Hyok Chol to insulate Choe Son Hui and more substantive diplomatic personnel, to a certain degree he is expendable and his superiors are not.”

The penalised members of Kim Yong Chol’s team included Kim Song Hye, who led the preparations, and Sin Hye Yong, a newly elevated interpreter for the Hanoi summit. They were said to have been detained in a camp for political prisoners, the newspaper said.

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The diplomatic source said Kim Song Hye’s punishment seemed inevitable because she was a “prime author” of the North’s plan to secure sanctions relief in return for dismantling the Yongbyon main nuclear complex.

The idea was rejected by the United States which demanded a comprehensive roadmap for denuclearisation.

Kim Song Hye had also worked closely with Kim Yo Jong, the North Korean leader’s younger sister and a senior party official whom Kim Song Hye accompanied to South Korea for the Winter Olympics last year.

Kim Yo Jong was also lying low, the paper reported, citing an unidentified South Korean government official.

Madden, however, said Kim Yo Jong’s status was unchanged as Kim Jong Un’s top aide, citing her attendance at key party meetings in April and appearance in state media reports.

Sin Hye Yong was charged with making critical interpretation mistakes that included missing an unspecified “last-minute offer” the North Korean leader supposedly made as Trump was about to walk out, Chosun reported.

‘TWO-FACED’

North Korea’s official party mouthpiece Rodong Sinmun warned on Thursday that “two-faced” officials would face the “stern judgment of the revolution”.

“It is an anti-Party, anti-revolutionary act to pretend to be revering the leader in front of him when you actually dream of something else,” it said in a commentary.

Hong Min, a senior fellow at the Korea Institute for National Unification in Seoul, said it was possible Kim Hyok Chol and other officials faced some penalty but further verification was needed.

“Executing or completely removing people like him would send a very bad signal to the United States because he was the public face of the talks and it could indicate they are negating all they have discussed,” Hong said.