GENEVA -- North Korea insisted Tuesday it would never give in to "unreasonable" international resolutions against its nuclear arms program, insisting the prospects of denuclearising the Korean peninsula were deteriorating in the face of US hostility.

"The US and their followers are sadly mistaken if they miscalculate the DPRK (North Korea) would accept the entirely unreasonable resolutions against it," Jon Yong Ryong, the first secretary of North Korea's mission in Geneva, told the UN Disarmament Forum.

"The DPRK will never be bound to any resolutions," he said. 

His comments came after North Korea on Tuesday staged its most powerful nuclear test yet, claiming a breakthrough with a "miniaturised" device in a striking act of defiance which sparked an international outpouring of condemnation.

Jon hailed the test, which he said was "conducted in a safe and perfect way," and which he insisted was "part of practical measures as counter-action to defend the country's security and sovereignty in the face of the ferocious hostile act of the US".

The test, he said, would "greatly encourage the army and the people of the DPRK in their efforts to build a thriving nation... and offers an important occasion in ensuring peace and stability on the Korean peninsula and the region."

As for international diplomatic efforts to turn the arms race around, Jon insisted "the prospect for the denuclearisation of the Korean peninsula has become gloomier due to the US hostile policies to the DPRK that have become ever more pronounced."

He also criticised the European Union for not working impartially to bring an end to the nuclear stand-off.

If the "EU truly wants peace and stability on the Korean peninsula, it should urge the US first to terminate its hostile policy towards the DPRK on an impartial basis," he said.

Jon was especially searing in his criticism of Japan, whose Prime Minister Shinzo Abe was quick to condemn the nuclear test as "extremely regrettable."

The North Korean envoy said the criticism stemmed from "the base nature of the Japanese (to dislike) when things go well in other countries," calling Japan a nation of "fault-finders whose way of thinking is not normal."