Satellite images have emerged that appear to show activity at one of North Korea's submarine bases days after it threatened to carry out a missile test towards US-owned Guam.
This comes just a day after open warning by the American President Donald Trump saying-things will happen to the country like it "never thought possible" if Pyongyang thinks about attacking America or any of its allies.
On Aug. 5, the United Nations Security Council voted unanimously for fresh sanctions on North Korea, after it launched two ICBM tests last month, which has prodded Pyongyang to threaten a missile strike around the USA territory of Guam.
Recent satellite photos suggests that North Korea is preparing for fresh submarine-based missile tests, an expert has said, amid heightened tension between the USA and North Korea over the communist state's successful launch of an inter-continental ballistic missile.
Earlier, the United States President Donald Trump had issued a warning to North Korea that the USA military is "locked and loaded" to deal with any provocation from Pyongyang.
Military experts have suggested that, the North could be preparing for an upgrade to its existing submarine's launch systems Pukguksong-1.
The Pukguksong-1 is a SLBM, whose first successful test dates back to 24 August 2016.
The Pentagon has said that the United States and North Korea would proceed as planned with a joint military exercise despite the risk it will further antagonise the situation.