North Korea's state media on Sunday said leader Kim Jong-un inspected the loading of a hydrogen bomb into a new intercontinental ballistic missile, a claim to technological mastery that some outside experts will doubt but that will raise already high worries on the Korean Peninsula.
Another threat is deemed to be looming ahead as North Korean leader Kim Jong Un has been spotted inspecting a new, ultra explosive hydrogen bomb.
Melissa Hanham of the Middlebury Institute for International Studies in California said the images could not be proved real of themselves.
"It doesn't need to be shaped like that on the outside, but they threw in a diagram, just so we would get the message". But this test and North Korea's claims did point to the fact that the reclusive regime was not content with fission bombs alone-thermonuclear weapons were its real developmental goal.
That launch came after Pyongyang tested two intercontinental missiles in July and claimed to have a range of about 10,000km that could hit many parts of the mainland US.
South Korea's main spy agency has previously asserted that it does not think Pyongyang now has the ability to develop miniaturized nuclear weapons that can be mounted on long-range ballistic missiles.
Hydrogen or H-bombs, also known as thermonuclear weapons, work on fusion and are far more powerful, with a nuclear blast taking place first to create the intense temperatures required.
Electromagnetic pulse is an intense wave of electrical energy generated by the detonation of a nuclear weapon. It says its weapons programs are needed to counter US aggression.
Sunday morning, President Donald Trump said in a series of tweets that North Korea was "a rogue nation" that has become "a great threat and embarrassment to China". One blast could knock out power and communications over hundreds or even thousands of kilometers, the report said. North Korea wants to demonstrate it knows what makes a credible nuclear warhead.
Quake measuring 5.2 strikes North Korea, suggesting nuclear test
The depth of the quake was recorded as zero meters, the China natural disaster administration said, according to Reuters. Questions remain over whether Pyongyang has miniaturized its weapons and whether it has a working hydrogen bomb.
North Korea is believed to have conducted a test after a magnitude 5.7 natural disaster was detected earlier Sunday. The event was regarded as significant progress for the country's program on nuclear and missiles since the current leader has risen to power, subsequent to his father's death back in 2011.
It flew a Hwasong-12 over northern Japan last week, the first such overflight by a missile capable of carrying nukes, in a launch Mr Kim described as a "meaningful prelude" to containing Guam, the home of major U.S. military facilities, and more ballistic missile tests targeting the Pacific.
"This regime has signaled its contempt for its neighbors, for all members of the United Nations, and for minimum standards of acceptable global behavior", Trump said. "We know a conflict, a military conflict, in the area would be catastrophic".
South Korea's military said the first quake "appeared to be manmade".
Saturday, the United States and South Korea announced they have agreed "in principle" to revise a bilateral treaty that limits the weight and range of the South's ballistic missiles.
North Korea's state broadcaster says an important announcement is coming at 3 p.m.in Pyongyang.
Trump's administration is now pursuing what it calls a strategy of "peaceful pressure" to get North Korea to bring its nuclear weapons program to the negotiating table.
The North has previously claimed to have miniaturised a nuclear weapon, but experts have cast doubt on this.