"The matchless bravery and mass heroism displayed by soldiers of the Korean People's Army, involved in the overseas military operations, must be imposingly etched in history as a banner of invincibility," Kim said on Friday as he inspected the site, the Korean Central News Agency (KCNA) reported.

Russia's ambassador to North Korea attended a groundbreaking ceremony of the so-called Memorial Museum of Combat Feats in October, with Kim at the time hailing a "historic peak" in ties with Moscow.

The KCNA report on Saturday did not mention Russia. Earlier this week, however, Kim pledged to "unconditionally support" all of Russian President Vladimir Putin's policies and decisions, in a letter shared by KCNA.

North Korea, one of the world's most diplomatically isolated nations, has deepened ties with Moscow since it invaded Ukraine in February 2022.

It has dispatched thousands of troops to fight for Russia, according to South Korean and Western intelligence agencies, as Moscow presses ahead with its nearly four-year invasion of Ukraine.

At least 600 North Korean soldiers have been killed and thousands more wounded, according to estimates from South Korea.

In addition to sending troops to fight for Russia, Pyongyang has sent artillery shells, missiles and long-range rocket systems.

In return, Russia is sending North Korea financial aid, military technology and food and energy supplies, analysts have said.