South Korea's foreign ministry summoned on Monday the Russian ambassador in Seoul in protest over what it has called the dispatch of North Korean troops to Russia for deployment in Ukraine and pledged a joint international response.

South Korean intelligence has found that North Korea has dispatched 12,000 troops including special operation forces to support Russia’s war against Ukraine, news reports said Friday, a development that could bring a third country into the war and intensify a standoff between North Korea and the West.

North Korea sending troops into combat would mark a dramatic escalation in the country’s involvement in the war in Ukraine.