North Korea is suspected of supplying arms to Russia since late last year in return for luxury goods including a trainload of white horses.
North Korean leader Kim Jong-un is thought to have used the prized steeds as gifts for his family and high-ranking officials.
An intelligence source said some of the horses were used in a recent military parade.
White horses carry powerful symbolism in North Korea, and Kim and his wife Ri Sol-ju have posed riding them through a winter landscape on Mt. Baekdu looking like a pair of tubby Elves from "Lord of the Rings."
Russian news media reported that 51 Orlov Trotter horses were exported to North Korea last year.
One source familiar with North Korean affairs said, "Trains between Russia and North Korea resumed in November last year after being halted for two years and the first things to be imported were luxury goods for the Kim Jong-un family and high-ranking officials instead of daily necessities for the people."
State media showed Kim and his "beloved" daughter Ju-ae riding on the Orlov Trotters during the military parade marking the 75th anniversary of the army on Feb. 8. The display led to speculation that Kim has chosen his daughter as his successor to the North Korean throne.
