North Korea has opened a memorial museum in Pyongyang for its soldiers killed while fighting alongside Russian forces in the war in Ukraine, in the clearest sign yet of how central the conflict has become to the growing alliance.

The inaugural ceremony at the Memorial Museum of Combat Feats at the Overseas Military Operations was held on Sunday. It also marked the first anniversary of what the two countries describe as the end of an operation to “liberate” Russia’s Kursk border region from a Ukrainian incursion, the state-run Korean Central News Agency (KCNA) reported on Monday.

KCNA said North Korea’s leader Kim Jong Un attended the event along with senior Russian officials, including State Duma Chairman Vyacheslav Volodin and Defence Minister Andrei Belousov.

South Korea’s intelligence agency has estimated that North Korea deployed about 15,000 soldiers to fight for Russia in the Kursk region, and that about 2,000 of them were killed. Moscow and Pyongyang have not disclosed any figures.

During the ceremony, Kim sprinkled earth over the remains of one soldier and laid flowers for others whose bodies had been placed in a mortuary, according to KCNA. Kim and the Russian officials then signed a guestbook at the newly opened museum.

In his speech, Kim said the fallen North Korean troops would remain “a symbol of the Korean people’s heroism” and would support “a victorious march by the Korean and Russian people”.

He accused the United States and its allies of pursuing a “hegemonic plot and military adventurism” on the Russia-Ukraine front, praising Russian and North Korean forces for thwarting those efforts.

Meeting Belousov separately, Kim pledged full support for Russia’s policy of defending its sovereignty and security interests, KCNA said.

Russia’s TASS news agency quoted Belousov as saying that Moscow is ready to sign a military cooperation plan with Pyongyang covering 2027-31.

In a letter read by Volodin, Russian President Vladimir Putin said the new museum would be “a clear symbol of the friendship and solidarity” between the two countries and pledged to further strengthen their “comprehensive strategic partnership”.

Since Russia’s full-scale invasion of Ukraine in 2022, Kim has tilted his foreign policy decisively towards Moscow, supplying troops and conventional weapons in exchange, analysts say, for economic support and possibly sensitive technologies.

Officials in South Korea, the US and allied countries fear Russia could transfer advanced know-how to Pyongyang that would boost its nuclear and missile programmes.

Military experts say North Korean troops initially suffered heavy losses in Kursk due to their lack of combat experience and unfamiliarity with the terrain, making them vulnerable to Ukrainian drone and artillery fire.

But Ukrainian military and intelligence officials have assessed that the North Koreans later gained crucial battlefield experience and became central to Russia’s efforts to overwhelm Ukrainian forces by deploying large numbers of soldiers in the region.