This photoraph taken on Dec. 22, 2022 shows a general view of the de-occupied city of Izyum, Kharkiv region, amid the Russian invasion of Ukraine. (AFP)

North Korea on Friday rejected accusations by Japan and the US that it transported munitions to Russia by rail.

“The DPRK remains unchanged in its principled stand on the issue of arms transaction between the DPRK and Russia which has never happened,” the nation’s state-run Korean Central News Agency said in an English-language statement citing a Foreign Ministry spokesperson.

The statement came after the Tokyo Shimbun reported the previous day that the North transported artillery shells and other munitions via train linking the North's northeastern border city of Rason with Khasan in neighboring Russia.

The KCNA called the report “the most absurd red herring, which is not worth any comment or interpretation.”

The White House also said North Korea delivered an arms shipment to a private Russian military company, the Wagner Group, for use in the war in Ukraine.

John Kirby, the National Security Council spokesperson, told reporters Thursday that North Korea completed an initial shipment of weapons to Russia, including infantry rockets and missiles last month.

"We can confirm that North Korea has completed an initial arms delivery to Wagner, which paid for that equipment," he said.