The U.S. Treasury Department has announced plans to sanction two corporations linked to Office 39 of North Korea’s Korean Workers' Party.

The two corporations designated for sanctioning by the department on Thursday are the Korea Daesong Bank and the Korea Daesong General Trading Corporation.

Under Secretary for Terrorism and Financial Intelligence Stuart Levey said in a statement that the two firms are “key components of Office 39's financial network supporting North Korea's illicit and dangerous activities."

The department describes Office 39 as a “secretive branch of the North’s government that provides critical support to North Korean leadership in part through engaging in illicit economic activities and managing slush funds and generating revenues for the leadership.”

The Treasury Department’s recent move comes after it slapped sanctions on the North Korean army’s reconnaissance bureau and its chief, Kim Yong-chol, as well as Office 39 and the Green Pine Associated Corporation. Green Pine is suspected of exporting torpedoes similar to the one that sank the “Cheonan” naval ship in March.