A new threat directed at America and Japan is certain to heighten fears of a North Korean nuclear strike.
The Hermit Kingdom's state agency today threatened to use nuclear weapons to "sink" Japan and reduce the United States "to ashes and darkness" for supporting new sanctions.
Pyongyang's Korea Asia-Pacific Peace Committee, which handles the North's external ties and propaganda, also called for the breakup of the Security Council, which it called "a tool of evil" made up of "money-bribed" countries that move at the order of the United States.
"The four islands of the archipelago should be sunken into the sea by the nuclear bomb of Juche. Japan is no longer needed to exist near us," the committee said in a statement.
The North also targeted the US directly. "Let's reduce the US mainland into ashes and darkness. Let's vent our spite with mobilisation of all retaliation means which have been prepared till now," the statement said.
The threat follows the release of satellite imagery taken just days after North Korea conducted its sixth nuclear test. The images show the secretive state may be preparing for another blast.
The images, released by US monitoring group 38 North, show new activity in alternate tunnel portal areas at the Punggye-ri test site including parked trucks, mining carts as well as other equipment.
According to 38 North, this could indicate Pyongyang may have another test in store.
"Such activity, coming shortly after the largest underground nuclear test conducted at Punggye-ri to date (via the North Portal), suggests that onsite work could now be changing focus to further prepare those other portals for future underground nuclear testing," it said.
"Onsite work could now be changing focus to further prepare those other portals for future underground nuclear testing."
The images, taken just five days after the September 3 test, also show a fresh crater which was potentially caused by its most recent test.
'BIGGER THAN HIROSHIMA'
The release of the images comes as it emerged North Korea's most recent nuclear test probably had a yield of 250 kilotons, much higher than official estimates.
The US Geological Service put the magnitude of the resulting earthquake at 6.3, and the Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) and Norwegian agency NORSAR had raised their initial figures to 6.1.
According to 38 North, it was raising its estimate for the yield of the blast to "roughly 250 kilotons".
The figure is more than 16 times the size of the 15-kiloton US bomb that destroyed Hiroshima in 1945.
"This large explosive yield is also quite close to what 38 North had previously determined to be the maximum estimated containable yield for the Punggye-ri test site," it said
Governmental estimates of the yield vary from South Korea's 50 kilotons to Japan's 160.
US officials are still assessing whether it was an H-bomb, also known as a thermonuclear weapon, but that "so far there is nothing inconsistent with the North Korean claim that this was a hydrogen bomb".
Satellite imagery captured by 38 North also showed numerous landslides around the Punggye-ri test site immediately following the test.
Just days ago, a Chinese scientist warned the mountain beneath where the six bombs exploded may be on the point of collapse.
Chinese nuclear weapons researcher and chair of the China Nuclear Society Wang Naiyan told the South China Morning Postit was a potential major environmental disaster in the making as the mountain has been weakened by the previous blasts.
Pyongyang claimed its sixth test showed a hydrogen bomb that could be fitted into a missile.
The test saw the United Nations Security Council adopt its eighth set of sanctions, despite previous resolutions failing to halt Pyongyang's weapons ambitions.
North Korea's foreign ministry condemned the new measures "in the strongest terms", calling them a "full-scale economic blockade" driven by the US and aimed at "suffocating" its state and people.
It was "another illegal and evil 'resolution on sanctions' piloted by the US", it said in a statement carried by the official KCNA news agency.
"The DPRK will redouble the efforts to increase its strength to safeguard the country's sovereignty and right to existence," the ministry said.
UN nuclear disarmament campaigner John Hallam told news.com.au satellite images are a good indication of what's going on at the test site.
However Hallam remained cautious about whether this indicated the DPRK was going to conduct a new test soon.
"I remind myself that at one point almost a year back when the analyst community, including 38 North, were confidently predicting a test, the North Koreans decided to play a game of baseball on top of the test site, conveniently timing the game for the passage overhead of the satellite," he said.
"They also put out a statement basically saying they'd have a test when Kim Jong-un felt like having one."
Hallam also pointed out it was difficult to how much damage has been done under ground by the most recent test.
"If the test was indeed one of 250Kt. it will be at or very close to, the capacity of the Mt Mantap site to accommodate," he said.
"A few tests like that would render the mountain too cracked to test in much more. It would have a much greater capacity for much smaller tests of the kind the DPRK had done to date."
Hallam also said all this didn't mean that Kim could mount such a warhead on his missiles right now although he could be capable of reaching this goal soon.
"All of this indicates to me that we'd be insane to go to war with the DPRK, and that whatever we think about the DPRK and Kim, war is not an option that sane people would want to go for," Hallam said.
"With two unstable and not very responsible individuals holding nuclear buttons and in charge of substantial nuclear arsenals, it's shaping up to be more and more terrifying."