Kim Hak-tune worked at the Pyongyang University of Science and Technology (PUST) and was hung on 6 May, state-run news organization KCNA said.
KCNA said that "a pertinent establishment" was "directing [a] nitty gritty examination" into Kim Hak-tune's claimed wrongdoings.
It gave no further subtle elements.
A State Department official said Washington was "mindful of reports that a US resident was confined in North Korea", including it would liaise with the Swedish Embassy in Pyongyang, which takes care of US interests in North Korea.
Kim Hak-melody had already portrayed himself as a Christian preacher who planned to begin a trial cultivate at PUST, Reuters news organization announced, refering to an online post by Mr Kim.
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