Seoul, Beijing defence officials discuss Pyongyang nuclear test

South Korean and Chinese defence officials met in Seoul today with North Korea's latest nuclear test high on the agenda, as pressure grows on Beijing to take a tougher line with ally Pyongyang.

The director-level talks are held every year, but were completely overshadowed this time around by the North's fourth nuclear test last week, which triggered global condemnation and the promise of fresh UN sanctions.

"The two sides will discuss the security situation on the Korean peninsula, as well as the wider region," a defence ministry official said.

The talks came two days after South Korean President Park Geun-Hye urged China to step up to the plate and support genuinely punitive sanctions that would help bring Pyongyang to heel.

"I believe China is aware that if its strong determination is not put into actual, necessary actions, we will not be able to prevent a fifth or sixth nuclear test," Park said.

China is North Korea's chief diplomatic protector and economic benefactor, but traditional ties have become strained as Beijing's patience has worn thin with Pyongyang's behaviour and unwillingness to rein in its nuclear weapons ambitions.

But China's leverage over Pyongyang is mitigated, analysts say, by its overriding fear of a North Korean collapse and the prospect of a reunified, US-allied Korea directly on its border.

US Secretary of State John Kerry has also urged China to take a stronger line with North Korea, warning in a call to his Beijing counterpart last week that it can no longer be "business as usual".

North Korea says the January 6 test was of a miniaturised hydrogen bomb -- a claim largely dismissed by experts who argue the yield was far too low for a full-fledged thermonuclear device.

But whatever the nature of the device, it was North Korea's fourth nuclear test since 2006, and further evidence of Pyongyang's intention to continue developing its nuclear weapons capability in the face of international censure.

Since taking office in early 2013, Park Geun-Hye has actively courted closer ties with Beijing, and sought to build a personal working relationship with President Xi Jinping.