The U.S. Department of Treasury's Office of Foreign Assets Control imposed new sanctions on six entities and identified four vessels as blocked properties related to the transport of North Korean coal.

The Dec. 8 actions were in response to the transportation and exportation of North Korean coal in violation of UN Security Council Resolution 2371, the Treasury said in a news release. Entities within China have continued to engage in activities that are prohibited by the resolutions, the release said.

"The [Democratic People's Republic of Korea] continues to circumvent the U.N. prohibition on the exportation of coal, a key revenue generator that helps fund its weapons of mass destruction programs," U.S. Treasury Secretary Steven Mnuchin said in the news release. "The North Korean regime often uses forced labor from prison camps in its mining industries, including coal, exploiting its own people to advance its illicit weapons programs."

Designated companies included Weihai Huijiang Trade Ltd., Always Smooth Ltd., Good Siblings Ltd., Silver Bridge Shipping Co-HKG, Korea Daizin Trading Corp. and Thinh Cuong Co. Ltd. Vessels that loaded coal directly from North Korean ports and transported cargo throughout the region that were identified as blocked property included vessels named Calm Bridge, Asia Bridge, Lucky Star and Star 18.

Regulations generally prohibit U.S. entities from being involved in business dealings involving any property or interests in property of blocked or designated persons. Any foreign financial institutions that knowingly facilitate significant transactions for those designated could be subject to secondary sanctions from the U.S.