The powerful sister of North Korean leader Kim Jong Un on Friday denied widespread allegations that Pyongyang is shipping weapons to Russia, calling the claim "absurd".

South Korea and the United States have repeatedly accused North Korea of supplying weapons to Moscow, despite a raft of UN sanctions on both countries that would ban any such arms transfers.

Analysts have also warned that ramped-up testing and production of artillery and cruise missiles by the nuclear-armed North could be in preparation for shipments to Russia for use in Ukraine.

But Kim Yo Jong said Pyongyang had "no intention to export our military technical capabilities to any country," according to a statement carried by the official Korean Central News Agency on Friday.

She further accused Seoul and Washington of "misleading the public opinion with a false rumour that the weapon systems produced by ... (us) are 'for export to Russia'".

"What is most urgent for us is not to 'advertise' or 'export' something, but to make the war readiness and war deterrent of our army more perfect in quality and quantity," she said.

The largely isolated North has recently bolstered military ties with Moscow, and Pyongyang thanked Russia last month for using its UN Security Council veto to block the renewal of a panel of experts that monitored international sanctions on Kim's regime.

South Korea asserted in March that North Korea had shipped around 7,000 containers of arms to Russia for its war with Ukraine, transfers Seoul believes began around last July.

Washington and experts have said Pyongyang was seeking a range of military assistance from Russia in return, such as satellite technology and upgrading its Soviet-era military equipment.

The North last week said the country would equip its military with a new 240mm multiple rocket launcher starting this year, adding a "significant change" for the army's artillery combat capabilities was under way.

On Tuesday, leader Kim Jong Un inspected a new tactical missile weapons system and called for an "epochal change" in war preparations by achieving arsenal production targets.

"Tactical weapons including multiple rocket launchers and missiles shown by us recently are produced to discharge the only one mission," Kim Yo Jong's Friday statement said.

"We don't conceal the fact that such weapons will be used to prevent Seoul from inventing any idle thinking."

Inter-Korean relations are at one of their lowest points in years, with Pyongyang declaring South Korea its "principal enemy".

It has jettisoned agencies dedicated to reunification and threatened war over "even 0.001 mm" of territorial infringement.