The US Treasury named Daedong Credit Bank, "its front company" DCB Finance Limited and its China-based representative Kim Chol Sam for sanctions that freeze the assets of those designated "proliferators of mass destruction" and their supporters.
It also set sanctions on Son Mun San, the external affairs bureau chief of North Korea's General Bureau of Atomic Energy, who has directed nuclear-research efforts.
The Treasury said the new designations build upon US efforts to target financing for North Korea's ballistic missile and weapons of mass destruction programs.
Daedong Credit Bank was providing financial services to the Korea Mining Development Trading Corporation, Pyongyang's premier arms dealer as well as its main financial arm, and the Tanchon Commercial Bank, the Treasury said.
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Both KOMID and TCB were previously designated for US and United Nations sanctions.
Since at least 2007, the Treasury said, Daedong Credit Bank has handled hundreds of financial transactions worth millions of dollars on behalf of KOMID and TCB, at times hiding those transactions.
DCB Finance Limited is registered in the British Virgin Islands and also operates out of China.
The sanctions prohibit transactions with any US person and freeze any assets on US soil.