Mystery still surrounds the whereabouts of North Korea's leader Kim Jong-un, who has not been seen in public for more than a month.

The 31-year-old dictator was last seen in public at a concert in Pyongyang on September 3.

In July he had an obvious limp at an event marking the 20th anniversary of the death of his grandfather, North Korea's founder Kim Il-sung.

His public absence has fuelled speculation that he is suffering from bad health.

Late last month, North Korean state media said Mr Kim was suffering from "discomfort" but gave no further explanation for his absence.

Remco Breuker, professor of Korean studies at Leiden University in the Netherlands, said Mr Kim's disappearance may signal a power shift within the North Korean elite, and the dictator could have been placed under house arrest.

"We're not sure where he is, or what's happening. We don't know whether he's in the hospital or whether he's been put under house arrest," Professor Breuker told the ABC.

"The one thing that we can be sure of is the North Korean propaganda has for the last year or so, tried to portray him in a different light.

"They've tried to make him more human, less of an almost super-human, supreme leader. And I think all signs point to a situation where we may well have a North Korean regime without Kim Jong-un as its nominal head."

North Korean leader Kim Jong-un has not been seen in public since September. ( AFP: Korean Central News Agency )

Professor Breuker said he was concerned that behind-the-scenes powerbrokers could push Mr Kim to take the fall for North Korea's poor human rights record.

"No matter who is in charge nominally, the North Korean system remains the same," he said.

"Kim Jong-un's never been in charge, it's the people behind him. The old friends of his fathers. Those are the people in charge.

"What I am afraid of is that what they'll do is by putting all the blame on Kim Jong-un, it's cleansing themselves of any blame so they can continue ruling North Korea."

Jasper Kim, the CEO of the Asia Pacific Global Research Group, said he believes a recent visit by North Korean officials to South Korea was designed to confuse the West.

North Korea sent its most senior delegation ever to its estranged neighbour on Sunday, raising hopes of improved relations between the two.

"Perceived confusion and chaos, both domestically and internationally, by the international community, is exactly what North Korea wants since it increases the risk profile of the country," he said.

"From the perspective of the US, South Korea, China and other players, [it] increas[es] the stakes of the negotiation game."