Singapore (CNN) If North Korea's leader Kim Jong Un has executed a top official over his handling of nuclear talks in Hanoi, the US' top North Korea diplomat said he hasn't gotten word.

"I don't know," US Special Representative to North Korea Stephen Biegun said Saturday, when asked about reports that Kim Hyok Chol, North Korea's special envoy to the US, was executed after Kim and US President Donald Trump failed to reach an agreement at their second summit in February.

Instead, Biegun directed CNN to comments made by Secretary of State Mike Pompeo in Germany on Friday.

Kim Hyok Chol (R), the North Korean leading negotiations with the United States, arrives at Hanoi's international airport on Feb. 20, 2019.

Pompeo said the US was looking into a report by the South Korean newspaper Chosun Ilbo. The paper -- quoting unnamed North Korean sources -- said Kim Hyok Chol was executed in March at the Mirim airport in Pyongyang on charges of "being recruited by US imperialists and betraying the supreme leader." CNN has not been able to independently verify the reporting in Chosun Ilbo -- South Korea's most circulated daily newspaper -- and South Korean reports of North Korean executions have at times been inaccurate.

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