North Korea's Kim Jong Un oversaw the test-firing of a 240mm multiple rocket launcher equipped with a new "guiding system", state media said on Wednesday, as Pyongyang continues to upgrade its arsenal.

The announcement comes about three months after North Korea said it would equip its military with a "new" 240mm multiple rocket launcher known to be capable of striking Seoul and nearby areas.

The isolated, nuclear-armed country has recently bolstered military ties with Moscow, and analysts have said the North could be testing and ramping up production of artillery and cruise missiles before sending them to Russia for use in Ukraine.

The United States and Seoul have accused North Korea of supplying ammunition and missiles for Russia's war effort, a claim Pyongyang has called "absurd".

The multiple rocket launcher, "technically updated in its manoeuvrability and concentrated firing capability, was proved to be advantageous in all indices", Pyongyang's official Korean Central News Agency said on Wednesday.

Updates included "newly applied guiding system, controllability and destructive power," it said.

At the test-firing, Kim also "set forth an important policy to be pursued in producing new artillery pieces and equipping army units with them", it added without providing details.