Kim Yong Chol, the North's counterpart to Secretary of State Mike Pompeo in the nuclear negotiations, was sent to a labour camp after the Kim-Trump summit in Hanoi in February, South Korea's Chosun Ilbo newspaper had reported Friday.

The paper had also made worldwide headlines by saying that Kim Hyok Chol, North Korea's special envoy to the United States, had been executed by firing squad in March, after the two leaders failed to come to a deal over sanctions relief and the North's nuclear programme.

Kim Hyok Chol was Pyongyang's counterpart to US special representative Stephen Biegun in the run-up to Hanoi, and the Choson Ilbo said he had been put to death for "betraying the Supreme Leader" after he was "won over to the US" during pre-summit negotiations.

But the North is difficult to report on as one of the world's most isolated nations and some previous Southern reports of purges and executions by Pyongyang have later proved inaccurate.

On Monday, the North's official Rodong Sinmun newspaper carried a picture showing Kim Yong Chol sitting five seats down from North Korean leader Kim Jong Un, with both his hands covering his face, at a "performance given by amateur art groups of the wives" of military officers.

The South's Munhwa Ilbo afternoon paper carried the photo on the front page of its Monday edition, with the headline: "Kim Yong Chol, rumoured to be purged, affirms his position next to Kim Jong Un".

But there was no sign of Kim Hyok Chol, the official said to have been executed, in the Rodong Sinmun picture, nor was he mentioned in the official Korean Central News Agency's report on the event.

- 'Likely to be false' -

Chung Seong-chang, a senior researcher at the private Sejong Institute, said Pyongyang had probably issued the report and pictures in response to the Choson Ilbo report.

Kim Yong Chol had not been seen in public for some time, but rather than being purged he had undergone surgery to remove a malignant tumour, Chung said, adding he obtained the information from a person who regularly contacts North Koreans.

South Korea's parliamentary intelligence committee in April said Kim Yong Chol had been censured over his handling of the Hanoi summit, despite the fact he had recently been named a member of the State Affairs Commission, a supreme governing body chaired by Kim Jong Un.

The report of Kim Hyok Chol's execution was "likely to be false", Chung said, citing information he had received that Kim was seen in mid-April -- although he declined to disclose his source.

"No one would dare to take part in nuclear talks if Kim Jong Un sends officials to hard labour, political prison camp or executes them if talks fail," he said.