North Korea's foreign ministry denied a media report it supplied munitions to Russia, calling it "groundless", the North's official KCNA news agency reported on Friday.
The North also condemned the US for providing lethal weapons to Ukraine.
Earlier, Japan's Tokyo Shimbun reported that North Korea had shipped munitions, including artillery shells, to Russia via train through their border last month. It added that additional shipments were projected to come in the coming weeks.
"The Japanese media's false report that the DPRK offered munitions to Russia is the most absurd red herring, which is not worth any comment or interpretation," a ministry spokesperson said in a statement carried by the KCNA.
The White House indicated that the North completed an initial arms delivery to a private Russian military company, the Wagner Group, to help boost Russian forces in Ukraine.
In response, the North Korean spokesperson said: "The DPRK remains unchanged in its principled stand on the issue of 'arms transaction' between the DPRK and Russia which has never happened."
Washington is "bringing bloodshed and destruction to Ukraine by providing it with various kinds of lethal weapons."