UN Secretary-General Ban Ki-moon has called North Korea’s fourth nuclear test “deeply troubling” and “profoundly destabilising for regional security”, while diplomats said the Security Council would have to consider new sanctions steps.

“This test once again violates numerous Security Council resolutions despite the united call by the international community to cease such activities,” the United Nations chief told reporters on Wednesday.

“It is also a grave contravention of the international norm against nuclear testing.”

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“I demand the DPRK (North Korea) cease any further nuclear activities and meet its obligations for verifiable denuclearisation,” he said.

North Korea said it had successfully conducted a test of a miniaturised hydrogen nuclear device on Wednesday morning, marking a significant advance in the isolated state’s strike capabilities and ringing alarm bells in Japan and South Korea.

The 15-nation Security Council was holding an emergency meeting to weigh a possible response to what diplomats described as Pyongyang’s latest provocation. The meeting was requested by the United States and Japan.

“We plan to work with other countries so that a resolution with strong content can be adopted at the UN Security Council as swiftly as possible,” Japanese Foreign Minister Fumio Kishida told reporters.

Japan is a temporary member of the council for the next two years.

Several Western diplomats said that if the latest North Korean nuclear test was confirmed, the United States, European council members and Japan would seek to expand existing UN sanctions against Pyongyang.

Pyongyang has been under UN sanctions due to its nuclear weapons program since it first tested an atomic device in 2006.

– AAP