North Korea on Friday slammed US allegations that its space research is essentially a disguised ballistic missile programme, and vowed to send more satellites into orbit in defiance of UN sanctions.

Dismissing the "litany of rubbish" put out by the US "barking dogs," the North's National Aerospace Development Administration (NADA) said it would push forward with a robust space launch agenda.

Coming just days after North Korean leader Kim Jong-Un called for more satellite deployments, the NADA statement will fuel speculation that the nuclear-armed North is planning a long-range rocket launch in the coming months.

North Korea successfully put a satellite into orbit with its Unha-3 carrier in December 2012.

That launch was condemned by the international community as a disguised ballistic missile test and resulted in a tightening of UN sanctions.

"No one... should any longer misinterpret the entirely just space development of (North Korea) and float wild rumours about it," the NADA statement said.

"No matter who dares grumble and no matter how all hostile forces challenge the launch, (our) satellites... will soar into space one after another at the time and place designated and decided by the supreme leadership," it added.

Satellite analysis has shown a major construction programme underway at North Korea's Sohae Satellite Launching Station since mid-2013, focused on upgrading facilities to handle larger, longer-range rockets with heavier payloads.

The US-Korea Institute at Johns Hopkins University believes the completed upgrade would allow the Sohae site to handle rockets of up to 50 metres (165 feet) in length -- almost 70 percent longer than the Unha-3.

But such a rocket is still believed to be several years from becoming operational, meaning a repeat Unha-3 launch would be more likely in the short-term.

The 2012 satellite launch was seen as a major step forward for the North's nuclear weapons programme, as long-range missile delivery capability had long been cited as its main weakness.

There is little doubt that the North has an active ballistic missile development programme, but expert opinion is split on just how much progress it has made.

The North has yet to conduct a test showing it has mastered the re-entry technology required for an effective intercontinental ballistic missile.