South Korea's foreign ministry summoned Russian Ambassador Georgiy Zinoviev on Monday to strongly protest the deployment of North Korean troops to Ukraine. Vice Foreign Minister Kim Hong-kyun condemned the "illegal military cooperation in the strongest terms," warning that "all available means will be mobilized" against actions threatening Seoul's "core security interests." Russia swiftly countered, stating that Moscow's cooperation with Pyongyang adheres to international law and does not jeopardize South Korean security interests.

The spat comes months after Seoul's top security official warned of potentially providing lethal weapons to Ukraine should Russia cross a "red line." However, Seoul remained vague on Monday about whether it will do so, with the defense ministry spokesperson stating that the government is "open to various possibilities" for response.