NORTH Korea is "readying two intercontinental ballistic missiles" to figuratively "nuke" Donald's Trump inauguration, it's been reported.
Military officials say the rogue state wants to send a "strategic message" to the incoming US President by timing launches to ruin his big day on Saturday (AEDT).
In a statement, South Korea's Joint Chief of Staff said the reports could not be confirmed but said the military was monitoring the situation closely.
However, according to news reports in South Korea two missiles have already been placed on mobile launchers.
The devices "are estimated to not exceed 15m in length, making them shorter than the North's existing ICBMs."
An ICBM test in the coming days is "highly plausible," Andrei Lankov, a professor at Seoul's Kookmin University, told CNN.
"Judging by earlier behaviour they usually like to greet a newly elected American president with some kind of nice surprise like a nuclear (test) or missile launch," he said.
"Because President-elect Trump tweeted that 'it won't happen,' such a launch could be seen as a serious humiliation for (the US)."
The news comes as satellite imagery shows increased activity at a major North Korean nuclear site, according to a new report.
Any potential ICBM test, while a propaganda win for Pyongyang, would also reveal a great deal about the progress of North Korea's weapons program.
Military experts predicted that any test would only involve a missile with a range of under 2500km, less than half the usual ICBM range of 5500km.
US-based monitoring project 38North said evidence suggested Pyongyang may also be preparing to resume operations at a plutonium production reactor at the Yongbyon Nuclear Scientific Research Center 90km north of the capital.
"Stepped-up activities throughout the Yongbyon Nuclear Scientific Research Center indicate that it is operating at a level somewhat above what has been observed during the past five years," the report said.
"The exact implications of that activity remain unclear except to reaffirm that the Yongbyon facility remains the centre of North Korea's nuclear program."
Plutonium from the Yongbyon reactor is believed to have been used in North Korea's nuclear weapons tests, according to a US government report.
Traditional nuclear weapons use plutonium (or uranium) as their main fuel. The "Fat Man" bomb the US dropped on Nagasaki used 14 pounds of plutonium, producing a blast equivalent to about 21,000 tonnes of TNT.
The threat comes after it was revealed Kim Jong Un's military will have nuclear warheads capable of striking US territory within a year.
Since taking power the North Korean dictator has dramatically increased his country's nuclear weapons program.
According to 38North, his Musudan missiles - with a range of 5600km - will be ready within a year.
The US has announced it will deploy its state-of-the-art THAAD advanced missile defence system in South Korea in eight to 10 months to combat the threat from the North.
Trump has vowed to tackle the North Korean 'problem' once in power.
"North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the US It won't happen!" Trump tweeted last month.
It was not clear what Trump meant: whether he believed North Korea was incapable of developing a reliable ICBM, or that the US would prevent it doing so.
The rogue state caused international uproar after it conducted its fourth nuclear test in January and fifth in September in defiance of furious international reaction and stiff sanctions.
The North's hard line message comes as a new US administration to be led by Trump will take office on Friday.