The recent nuclear test was the sixth and most powerful test North Korea has conducted since its first in 2006.

Following Monday's UN Security Council vote in support of the US-drafted sanctions resolution aimed at forcing the North Korean supreme leader Kim Jong-un to abandon the nuclear weapon and missile programmes, Pyongyang vowed to redouble its efforts to acquire weapons of mass destruction and warned that the USA would face "the greatest pain it ever experienced in history" for leading a push for harsher UN sanctions. The sanctions also ban textile imports from North Korea ― a vital industry in the Hermit Kingdom.

"Japan is no longer needed to exist near us", the state-run Korean Central News Agency said on Thursday, citing a statement by the Korea Asia-Pacific Peace Committee.

The watchdog noted Tuesday that images appeared to show two white vehicles near the north portal of the test "and their presence could be indicative of a post-test inspection effort".

Although experts have now concluded the latest nuclear test yielded an estimated 250 kilotons blast which is believed to be the maximum yield the Punggye-ri can contain. That would be much higher than most official estimates, which have varied.

North Korea has reportedly resumed work at its underground nuclear testing site, according to defense analysts, in a brazen act of defiance against the latest United Nations sanctions. "If it proves it can live in peace, the world will live in peace with it", she said.

The South Korean military said the air-to-surface Taurus missile was sacked from an F-15 fighter jet, then traveled through obstacles at low altitudes before precisely hitting a designated target over the sea off the country's western coast.

On the same day, South Korea announced it had conducted its first live-fire drill for an advanced air-launched cruise missile that would strengthen its pre-emptive strike capability against North Korea in the event of crisis.

Moon said just because the United States and South Korea were now pursuing a firm path of sanctions and military drills, the time for negotiations wasn't over.

It also increases the danger of the regime's ballistic missile program. Those three prongs - ground, air, and submarine - constitute what the military calls its nuclear triad.

"This is in order to make the right conditions for dialogues and I would like to emphasize this", he said.

"These disturbances are more numerous and widespread than seen after any of the North's previous five tests, and include additional slippage in pre-existing landslide scars and a possible subsidence crater", the report says.