The spy agency said, "North Korea has recently decided to send a total of 12,000 troops, including special forces, in four brigades to the Ukraine war."
The deployment marks the first time the renegade country has sent ground forces on such a large scale.
President Yoon Suk Yeol immediately called up top security officials for an emergency meeting to discuss the matter at the presidential office in Yongsan, Seoul.
He expressed grave concerns over the deepening military ties between Russia and North Korea from military supplies to troop deployment, posing a threat not only to South Korea but also to the international community.
Earlier in the day, Ukrainian President Volodymyr Zelenskyy said, "We know about 10,000 soldiers of North Korea, that they are preparing to send to fight against us."
