A South Korean foreign affairs official who spoke on the condition of anonymity said the ministry was "told by the U.S. State Department and the National Security Council that the report was groundless", though which part of the story was wrong wasn't specifically mentioned.
Kim's wife said her husband had been teaching agricultural techniques at Pyongyang University of Science and Technology.
Last month, North Korean officials detained Pyongyang University accounting professor Kim Sang Dok.
Song's warnings of war come after North Korea arrested a second USA citizen and professor from the evangelical-funded Pyongyang University of Science and Technology, bringing its total of US prisoners to four.
The KCNA said that Devandas Aguilar met with key North Korean officials including health minister Kang Ha-guk and Ri Hung-sik, a roving ambassador. "These biochemical substances were to be provided with the assistance of the CIA. while the South Korean Intelligence Service was going to provide necessary support and funding for this attempt at assassination on our supreme leader". "Finally, detaining an American citizen both limits possible US military escalation and can possibly be used to leverage negotiations if Pyongyang wants to open a diplomatic channel to the U.S".
North Korea claims the primary suspect is a man it has identified only by the ubiquitous surname "Kim".
Mr Fowle said: "I advise anyone planning personal travel to North Korea to seriously reconsider their plans".
Kim Hak Song is now the tenth American to be detained by North Korea's current leader, Kim Jong-un. The US doesn't deal diplomatically with Pyongyang. It says he is a North Korean resident of Pyongyang who worked for a time in the Russian Far East.
On Sunday, Kim Hak-song became the fourth American citizen now detained by the repressive regime, on charges such as espionage and crimes against the state.
North Korea has not permitted current and former United Nations investigators on North Korea's human rights record to conduct on-site probes into the situation inside the country.
Choe Il, who took over the role in late 2016, warned that the United States will not be able to attack North Korea first, because all American strategic assets will be turned to ashes at the first sign of movement towards an attack. The children are all hand-picked by Kim Jong-un's regime to receive a Western education, according to BBC News.
Daniel Cormier and Jon Jones official for July rematch
He said: "I've had a lot of time away from the sport and a lot of time to reflect on how much this MMA career means to me". The bout will provide Cormier with the opportunity to avenge his sole career loss, which took place at UFC 187.