The upper house of Russian parliament on Wednesday ratified a treaty with North Korea envisioning mutual military assistance, a move that comes as the U.S. has confirmed the deployment of 10,000 North Korean troops to Russia.

The Pentagon declined to comment about the "extracurriculars" of the roughly 10,000 North Korean troops deployed to Russia.

“We understand that more than 10,000 North Korean troops are currently in Russia, and a significant number of them have moved to the frontline areas including Kursk,” Jeon Ha-kyou, a spokesperson for Seoul’s defence ministry, told a briefing, citing intelligence authorities.