North Korea says will stand by Russia until 'victory' in Ukraine

North Korean leader Kim Jong Un (centre L) before the test-fire of the new Hwasong-19 intercontinental ballistic missile (ICBM), at an undisclosed location in North Korea. [AFP]

North Korea will stand by Russia until its victory in Ukraine, Pyongyang's foreign minister said in Moscow Friday, as the United States warned thousands of North Korean troops could be sent to combat in the Ukraine conflict in the coming days.

North Korea's Choe Son Hui is on a visit to Moscow as the West believes up to 10,000 North Korean troops are on the brink of entering the more than two-year conflict on Russia's side.

US intelligence has said some North Korean forces have made their way to Russia's Kursk border region, with Washington and Seoul urging Pyongyang to withdraw its troops.

"We will always stand firmly by our Russian comrades until victory day," Choe declared in Moscow after talks with her Russian counterpart Sergei Lavrov.

She said North Korea had no doubt in the "wise leadership" of President Vladimir Putin, who signed a mutual assistance pact with Pyongyang this summer and massively warmed ties with the reclusive state.

Choe praised Moscow's offensive in Ukraine as a "sacred struggle".

She also vowed that North Korea will continue to develop its nuclear arsenal, with Pyongyang widely suspected of wanting nuclear technology from Russia in exchange for military support.

Neither country has denied the troop deployment reports, which Choe and Lavrov did not mention in their statements after their talks.

Lavrov did however laud "very close ties" between the two countries' "armies and special services".

"This will also make it possible to solve significant security tasks for our citizens and yours," he added, without giving details.

Moscow 'deeply grateful'

Lavrov said Russia was "deeply grateful" for North Korea's "principled stance" on Ukraine.

North Korea and Iran have emerged as Russia's main backers in Ukraine, with both believed to be supplying Moscow with military hardware.

"I really appreciate today's opportunity to talk frankly in a comradely manner," Lavrov said, evoking Soviet-style language.

Russia has resuscitated its Soviet-era relations with North Korea since sending troops to Ukraine, glorifying the two countries' past standoff against the West.

Lavrov and Choe unveiled a plaque at Moscow's Yaroslavsky railway station in honour of North Korean leader Kim Il Sung travelling to Moscow in 1949 to seek Soviet leader Joseph Stalin's backing to invade South Korea.

In a ceremony that included an orchestra, Lavrov said the unveiling of the plaque "underscores the respect and reverence with which we treat our common history and great predecessors".

He said Putin and North Korea's current leader Kim Jong Un now aim to "try to be worthy of the contribution to our friendship that was made by our predecessors".

Zelensky slams Western inaction

US Secretary of State Antony Blinken said Thursday it has not yet seen North Korean troops deployed against Ukrainian forces but that this could happen "in the coming days".

The United States on Friday announced it will provide an additional $425 million in military aid to Ukraine including air defence interceptors and munitions for rocket systems and artillery "to meet its most urgent needs".

Ukrainian President Volodymyr Zelensky in his nightly address Friday criticised Kyiv's allies for inaction as Ukraine pleads for permission to fire donated long-range missiles deep into Russia.

"Now we see every site where Russia is amassing these North Korean soldiers on its territory -- all their camps. We could strike preventively if we could strike long enough," he said.

"Instead of providing the long-range strike capability that is so necessary, America is watching, Britain is watching, Germany is watching," the president said.

"Everyone is just waiting for the North Korean military to start striking at Ukrainians," he added.

Zelensky also criticised China, which he said could block logistics between Russia and North Korea.

On Friday, Russia struck a police station in Ukraine's second-largest city of Kharkiv with S-400 missiles, killing a police officer and wounding 30 police and 10 civilians, regional police said.

'Explosive'

Choe vowed in Moscow that the country will not give up advancing its nuclear programme and accused the West of escalating tensions on the Korean Peninsula.

She spoke a day after North Korea announced it had test-fired one of its newest and most powerful missiles, in a move slammed by the West.

"I once again assure you that our country will in no way change course on the strengthening of its nuclear forces," she said.

"The security situation of our nation is in a very dangerous and unstable state because of the machinations of the US and its satellites," she said.

"The situation on the Korean Peninsula could become explosive at any time," she added.

Seoul has warned that Pyongyang's deployment could escalate security threats on the Korean peninsula and that Pyongyang is likely to ask for Russian technology transfers to aid its weapons programs.