North Korea is expanding a weapons plant that manufactures missiles used by Russia against Ukraine, according to new research from a US-based think tank.

"For the Republic of Korea, these actions pose a serious threat, as North Korean troops are gaining combat experience, which could present additional security challenges in the region in the future," Defense Minister Rustem Umerov said following his visit to South Korea.

South Korean President Yoon Suk Yeol met with Ukrainian Defense Minister Rustem Umerov in Seoul on Nov. 27 to discuss concerns over deepening military ties between Russia and North Korea, Yonhap News Agency reported.