The U.S. Department of the Treasury on Friday announced sanctions on an individual and three entities -- including a Russian commercial bank -- for alleged links with the nuclear program of the Democratic People's Republic of Korea (DPRK).

The Treasury said in a statement that the Russian-registered Agrosoyuz Commercial Bank is "knowingly facilitating a significant transaction" for Han Jang Su, the chief Moscow representative of the DPRK's Foreign Trade Bank (FTB).

Han, the Treasury added, is "an individual designated for weapons of mass destruction-related activities" in the DPRK.

The fresh round of sanctions also targeted Ri Jong Won, the deputy representative of FTB in Moscow, as well as two other entities it said are facilitating Pyongyang's "illicit financial activity."

Vowing to keep existing sanctions imposed by both the United Nations and the United States, U.S. Treasury Secretary Steven Mnuchin said "sanctions will remain in place until we have achieved the final, fully-verified denuclearization" in the DPRK.