A North Korean state media outlet has accused the United States of "jumping to conclusions" that the North would soon stage a nuclear test, adding to the confusion over its immediate intentions.

The US and its ally South Korea are "fussing over speculation" without knowing exactly what action the North plans to take, Tongil Sinbo, a Japan-based pro-North weekly magazine funded by Pyongyang, said in an editorial.

"The US and enemies, based on their own hypothesis and arguments, jumped to the conclusion that we would stage a third nuclear test," said the editorial dated Friday and posted on the North's official website, Uriminzokkiri.

"They are fussing over speculation without having a clue about what important state measures will be taken, including whether it will be a nuclear test or something worse than that," it said.

The North's top body, the National Defence Commission, announced on January 24 it would carry out a "high-level nuclear test" and further rocket launches, in a defiant response to tightened UN sanctions after its successful long-range rocket launch in December.

The nation's young leader Kim Jong-Un recently vowed to take "important state measures" and discussed a "great turn" in bolstering military capability.

Experts and Seoul officials, citing recent satellite imagery, say the impoverished but nuclear-armed state has completed preparations for another atomic test in a site in the northeast.

Tongil Sinbo said the North's actions were not intended to threaten anyone but only aimed at protecting its national interest in the face of threats from the US and ally South Korea.

South Korean officials could not immediately be reached by AFP for comment.

A Seoul official quoted by Newsis news agency described the remarks as an attempt to confuse the South and the US ahead of the imminent test.

"It's only wishful thinking that the North will not stage a third nuclear test," the unidentified official was quoted as saying.

"If the North genuinely decides to scrap a plan for a nuclear test, it will be announced by official state media like the Rodong Sinmun," said the official, referring to the ruling communist party's official newspaper.

The isolated communist state insists its widely-condemned rocket launch was a scientific mission aimed at putting a satellite into an orbit.

The US and many other countries viewed it as a disguised ballistic missile test banned under UN resolutions triggered by Pyongyang's previous nuclear and missile tests in 2006 and 2009.