The phoney messages, delivered as fake mobile phone alerts and social media messages, advised US military personnel an their families to evacuate the Korean Peninsula.
Neither how many received the hoax messages nor who was behind them is clear, the US Forces Korea (USFK) said.
The USFK posted a statement on its official Facebook page on Thursday making clear that the US military did not issue any evacuation-related alerts.
It has also instructed all US Department of Defence personnel and their family to confirm any evacuation-related communications before acting.
The fake evacuation alert came at a sensitive time, with tensions high after North Korea conducted its sixth and largest nuclear test on September 3.
The test and a series of missile launches have triggered a war of words between the US President and evil dictator Kim Jong Un.
Mr Trump has called Kim a “madman who doesn’t mind starving or killing his people”, declaring the tyrant will be “tested like never before”.
The declaration came in a tweet and followed a North Korean threat to detonate a nuclear weapon over the Pacific ocean.
Last week at a United Nations conference, Mr Trump continued his blistering rhetoric against the dictator, saying: “The United States has great strength and patience, but if it is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea. ‘Rocket Man’ is on a suicide mission for himself and for his regime.
“The United States is ready, willing and able. But hopefully, this will not be necessary.
“That’s what the United Nations is all about. That’s what the United Nations is for. Let’s see how they do.”
Kim’s aide hit back at Mr Trump for the dictator, adding that: “There is a saying that the marching goes on even when dogs bark.
“If he was thinking he could scare us with the sound of a dog barking, that’s really a dog dream.
“In Korean, a dog dream is one that makes little sense.”