South Korea's spy agency said Friday it believes North Korea has decided to send large-scale troops to support Russia in its war against Ukraine and has already begun deployment.The National Intelligence Service (NIS) said it has learned that the North has recently decided to send four brigades of 12,000 soldiers, including special forces, to the war in Ukraine.An NIS source said the mobilization of the troops has "already begun."It marks the first time Pyongyang has deployed such a large number of ground forces to the war.The North's deployment signals a major development in the military cooperation between Moscow and Pyongyang besides their suspected arms trade, already criticized by the international community.On Thursday, Ukrainian President Volodymyr Zelenskyy said North Korea is preparing to send around 10,000 soldiers to Russia, calling the development "a big problem."Zelenskyy suggested that Russia is relying on North Korean forces to compensate for its substantial troop losses, as many y oung Russians seek to avoid conscription.Source: Yonhap News Agency