Friday morning's nuclear test triggered a magnitude 5.3 earthquake and sent world leaders scrambling to condemn the North's latest act of aggression, as Kim Jong-un's isolated regime continues to defy international sanctions.

South Korean President Park Geun-hye said the North Korean leader was showing "maniacal recklessness" in ignoring the world's call to abandon his pursuit of nuclear weapons. US President Barack Obama said the test would be met with "serious consequences".

The test was a "grave threat to regional security and to international peace and stability," Mr Obama said in a statement, adding North Korea should face consequences for its "unlawful and dangerous actions."

Australia's Foreign Ministers Julie Bishop, speaking in London on Friday morning, said China needed to do more to curb North Korea's nuclear ambitions.

"This is extremely destabilising behaviour," she said. "It poses not only a regional threat but a global threat. We condemn in the strongest possible terms this further provocative act by North Korea, which is in flagrant breach of numerous Security Council resolutions.

"We will certainly be seeking China's response to this. China is an influence in North Korea, China has a special role to play given its proximity to the North Korean regime, so we will be working with other partners but also calling on China to do more to curb this provocative behaviour," Ms Bishop said.

"While North Korea is testing nuclear weapons and carrying out these nuclear and ballistic tests their people are suffering. The long-suffering people of North Korea need a regime that focuses on their needs not provocative behaviour that represents a global and regional threat."

China, North Korea's only major diplomatic ally, said it was resolutely opposed to the test and urged Pyongyang to stop taking actions that would further worsen the situation. It began emergency radiation monitoring along its north-eastern border shared with North Korea, state media reported.

US Defence Secretary Ash Carter also singled out China's influence.

"It's China's responsibility," he said. "China has and shares an important responsibility for this development and has an important responsibility to reverse it."

The North's official Korea Central News Agency said the nuclear test was retaliation against "US-led hostile forces" and showed "the toughest will of the [Workers' Party] and the Korean people to get themselves always ready to retaliate against the enemies if they make provocation".

The test underscores Pyongyang's continued defiance but also what analysts say is the ineffectiveness of tough trade and diplomatic sanctions imposed after its previous nuclear test in January.

"Sanctions have already been imposed on almost everything possible, so the policy is at an impasse," Tadashi Kimiya, a University of Tokyo professor specialising in Korean issues, told Reuters. "In reality, the means by which the United States, South Korea and Japan can put pressure on North Korea have reached their limits."

North Korea's repeated nuclear and ballistic missile tests also underline tensions between Pyongyang and Beijing, which has failed to rein in the Kim regime's behaviour. The instability on the Korean peninsula saw Seoul announce in July it would ask the US military to deploy its Terminal High Altitude Area Defense anti-missile system.

Chinese President Xi Jinping warned his South Korean counterpart Park during the G20 Summit in Hangzhou earlier this week, saying that "mishandling the issue" could "intensify conflicts" in the Korean peninsula.

With Nick Miller, Reuters