Russia has provided North Korea with anti-air missiles and air defence equipment in return for sending soldiers to support its war against Ukraine, according to a top South Korean official.

Asked what the North stood to gain from dispatching an estimated 10,000 troops to Russia, South Korea’s national security adviser Shin Won-sik said Moscow had given Pyongyang economic and military technology support.

“It is understood that North Korea has been provided with related equipment and anti-aircraft missiles to strengthen Pyongyang’s weak air defence system,” Shin told South Korean broadcaster SBS in an interview aired on Friday.

At a military exhibition in the capital, Pyongyang, North Korean leader Kim Jong Un on Friday called for developing and upgrading “ultra-modern” versions of weaponry, and pledged to keep advancing defence capabilities, state media reported.

Russia this month ratified a landmark mutual defence pact with North Korea as Ukrainian officials reported clashes with Pyongyang’s soldiers on the front lines.

The treaty was signed in Pyongyang in June during a state visit by Russian President Vladimir Putin. It obligates both states to provide military assistance “without delay” in the case of an attack on the other and to cooperate internationally to oppose Western sanctions.

South Korea’s National Intelligence Service told lawmakers this week that the troops deployed to Russia are believed to have been assigned to an airborne brigade and marine corps on the ground, with some of the soldiers having already entered combat, the Yonhap news agency reported.

The intelligence agency also said recently that North Korea had sent more than 13,000 containers of artillery, missiles and other conventional arms to Russia since August 2023 to replenish its dwindling weapons stockpiles.

Experts say Pyongyang could be using Ukraine as a means of realigning foreign policy.

By sending soldiers, North Korea is positioning itself within the Russian war economy as a supplier of weapons, military support and labour – potentially bypassing its traditional ally, neighbour and main trading partner, China, according to analysts.

Russia can also provide North Korea access to its vast natural resources, such as oil and gas, they say.

North Korean Foreign Minister Choe Son Hui recently visited Moscow and said her country would “stand firmly by our Russian comrades until victory day“.

North Korea said last month that any troop deployment to Russia would be “an act conforming with the regulations of international law”, but stopped short of confirming that it had sent soldiers.

The deployment has led to a shift in tone from Seoul, which had so far resisted calls to send weapons to Kyiv. However, President Yoon Suk-yeol indicated South Korea might change its longstanding policy of not providing arms to countries in conflict.