North Korea has threatened to "punish" Australian Foreign Minister Julie Bishop over comments to US media about Kim Jong-un.

In an interview with radio station Voice Of America last week, Ms Bishop criticised Mr Kim and his pursuit of nuclear weapons.

"Nuclear tests and missile launches needlessly risk accidents or reprisal," she said.

"It is a fact that no country [can] improve its economy or security by threatening its neighbours and by impoverishing its own people.

"[Kim Jong-un] can hardly claim the legitimacy as a leader when his regime continues to defy international expectations."

North Korea's KCNA news agency said the country's foreign ministry was angered that Ms Bishop "dared hurt the dignity of the leadership of the DRPK".

"She is not entitled to call for legitimacy, as she is no more than a stooge carrying out the US hostile policy toward the DPRK, and echoing others' sophism without her own foreign policy and view," it said.

"The DPRK will never pardon but resolutely punish anyone who dares slander the dignity of its supreme leadership."

It did not say what punishment would entail.

South Korea's Yonhap news agency reports that while the North usually bristles at outside criticism of its leader, it is rare for it to speak so directly against a top diplomat from Australia.

It says North Korea has made several military threats against South Korea over its alleged slander of its leader in recent years but they have not been followed by action.