South Korea's defense minister says he thinks North Korea will send around 12,000 soldiers to Russia in the near future.

Kim Yong-hyun told a parliamentary session on Thursday that the dispatched soldiers will mainly include special forces troops, engineers and artillery personnel.

South Korea's intelligence agency has said around 3,000 North Korean troops are believed to have already been sent to Russia.

Kim said the North Koreans are being disguised in Russian uniforms and are acting under Russian military command without any operational authority. He added that "mercenaries" would be an appropriate description of them.

Kim harshly criticized North Korean leader Kim Jong Un for selling his people's army as "mere cannon fodder" for "an illegal war of aggression."

South Korean Foreign Minister Cho Tae-yul noted that US Defense Secretary Lloyd Austin has confirmed that North Korea has sent troops to Russia.

Cho said he heard that Washington will soon announce its assessment of the matter based on a more detailed analysis.