The U.S. Treasury Department on Thursday slapped sanctions on two firms of the Democratic People's Republic of Korean (DPRK), accusing them of supporting the country's "illicit and dangerous activities."

The Treasury Department designated the two firms, Korea Daesong Bank and Korea Daesong General Trading Corporation, pursuant to a presidential executive order for being owned or controlled by Office 39 of the ruling Korean Workers' Party.

The department said Office 39 is a secretive branch of DPRK's ruling party that provides critical support to the country's leadership in part through engaging in illicit economic activities and managing slush funds and generating revenues for the leadership.

Office 39 has been previously put on the U.S. sanction list by the Treasury Department.

As a result of the designation, assets of the two firms within U.S. jurisdiction will be frozen and U.S. persons are prohibited from conducting financial or commercial transactions with them.