North Korea's Kim pledges 'invariable support' in Putin letter

North Korean leader Kim Jong Un promised his "invariable support" for Russia in a letter to President Vladimir Putin, calling Russia's ongoing war "sacred," state media reported Tuesday.

Since Russia launched its invasion of Ukraine in 2022, North Korea has become a key ally of the Kremlin, sending troops to support Moscow's war effort in return for economic benefits and military technology, analysts say.

South Korea's spy agency estimated last year that some 2,000 North Korean troops had been killed in the war, while a more recent assessment put the number of North Korean soldiers killed or wounded at around 6,000.

"Firmly convincing the victory of the Russian Federation in the present sacred war for defending the security interests of the country and international justice, I promise my invariable support to dear friend you and the fraternal Russian people," Kim said in the letter, according to the official Korean Central News Agency on Tuesday.

"The will of mine and the government of the Democratic People's Republic of Korea is firm without doubt to expand and deepen the joint work with the Russian Federation in a comprehensive way," he said, using the country's official name.

The letter comes amid speculation that Pyongyang is poised to send more troops to Russia to aid its war effort against Ukraine.

Kyiv has also said that up to 50,000 North Korean troops are due to deploy to Russia, although it has provided no evidence to back the claim or a timeframe for the deployment.

In making the claim, Ukrainian President Volodymyr Zelensky asked Seoul to supply air defence systems to protect against Russian missiles, a request that has gone unanswered by the South.