North Korea's Kim Jong Un visits missile bases, cites US nuclear threat

North Korean leader Kim Jong Un has visited missile bases to examine their readiness to undertake actions of "strategic deterrence", while calling US nuclear capabilities a growing threat to the country, state media reported on Wednesday.

The US strategic nuclear arsenal poses an "ever-increasing threat" to North Korea's security environment, which demands that Pyongyang maintain a strict counteraction posture of its nuclear forces, he was quoted as saying by KCNA.

North Korea has been stepping up its development of ballistic missiles and a nuclear arsenal, drawing international sanctions, and forming close military relations with Russia.

Kim's visit to the bases comes amid growing tensions with South Korea and its allies. This has included concerns over what Seoul says is a dispatch of North Korean troops to Russia to fight in Ukraine, a claim that has been denied by Pyongyang.

South Korea's National Security Adviser Shin Won-sik and Jacek Siewiera, the head of the Polish National Security Bureau, expressed concern over Pyongyang's military cooperation with Moscow during a meeting in Seoul.

The two also agreed to cooperate closely with the international community on the issue, according to a statement released by South Korea's presidential office.

In the KCNA report, Kim also called for the modernisation of the armed forces by giving priority to strategic missiles in the future, calling it "an important principle of the strategy for building national defence."

He was accompanied on his visit by Kim Yo Jong, his powerful sister, and Kim Jong Sik, the first vice department director of the Central Committee of the ruling Workers' Party of Korea, KCNA reported.

Photographs released by KCNA showed Kim dressed in a leather coat inspecting the missile bases.

KCNA did not specify when the visits took place