Kim Jong Un threw dirt over the remains of one dead soldier at the opening of a memorial museum for his compatriots who died fighting alongside Russia in the Ukraine war.
The North Korean leader was accompanied by Russian officials at the ceremony in the capital, Pyongyang, on Sunday.
It marked the one-year anniversary of the recapture of Russia's Kursk region, which Ukrainian forces had seized in an effort to relieve pressure on the frontline in parts of occupied Ukraine.
Bunches of white balloons floated overhead as soldiers in uniform stood to attention beside the graves of their comrades.
In a letter to Mr Kim read out during the ceremony, President Vladimir Putin said the museum "will undoubtedly be a clear symbol of the friendship and solidarity" between the two countries.
Pyongyang has not officially disclosed how many of its soldiers were deployed, but South Korea's intelligence service estimated last year that North Korea sent about 15,000 troops, 2,000 of whom were killed.
Experts have said North Korean troops sent to the war initially became easy targets for drone and artillery strikes due to their lack of combat experience and unfamiliarity with the theatre.
However, Ukrainian officials have stressed that the foreign fighters were gaining crucial battlefield experience and were key to Russia's strategy of sending overwhelming numbers of troops to their positions in Kursk.
North's Korean Central News Agency (KCNA) reported that Kim Jong Un attended the ceremony along with top visiting Russian officials including Vyacheslav Volodin, speaker of the State Duma, and defence minister Andrei Belousov.
Mr Kim threw dirt over the remains of one dead soldier and laid flowers before others, before he and Mr Volodin wrote in the guest book, KCNA reported.
The North Korean leader said the spirits of dead North Korean soldiers will remain as "a symbol of the Korean people's heroism" and support "a victorious march by the Korean and Russian people".
He praised the North Korean and Russian forces for thwarting what he called a US-led Western "hegemonic plot and military adventurism" on the Russian-Ukraine front.
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Mr Kim reportedly told the Russian defence minister that his country will fully support Russia in defending its security interests.
Russia's state news agency, Tass, cited Belousov as telling Kim that Russia was ready to sign a Russian-North Korean military cooperation plan for the 2027-2031 period.
(c) Sky News 2026: Kim Jong Un speaks at memorial for North Korean soldiers killed fighting for Russia
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