Ltd by the U.S. Attorney for the District of Columbia, represent two of the largest North Korea-related seizures the government has ever pursued.
North Korea has conducted two nuclear tests and dozens of missile tests since the beginning of past year, significantly raising tension on the heavily militarized Korean peninsula and in defiance of U.N. Security Council resolutions.
The Treasury Department, which oversees USA sanctions programs, said that those targeted by the sanctions had helped people known to support the North's nuclear and ballistic missile programs, or had traded in North Korean energy, exploited its workers or acted as a conduit to the worldwide financial system.
An FBI investigation into the company found that Dandong Chengtai is one of the largest importers of North Korean coal in China.
"[The] sanctions target third-country companies and individuals that assist already-designated persons who support North Korea's nuclear and ballistic missile programs, deal in the North Korean energy trade, facilitate its exportation of workers, and enable sanctioned North Korean entities to access the US and global financial systems", OFAC said in a news release.
Also sanctioned were Russian citizens Mikhail Pisklin, Andrei Serbin and Irina Huish for activities in the North Korean energy industry.
The sanctions will effectively block their targets from accessing much of the global financial system, as well as freezing any U.S. assets.
Moscow may be supporting Pyongyang
Ten Chinese and Russian companies as well as six individuals were named, some of whom are trading coal, oil and mineral resources with North Korea.
The sanctions target restrict dealings with Russian banks and energy companies. "We are taking actions consistent with United Nations sanctions to show that there are consequences for defying sanctions and providing support to North Korea, and to deter this activity in the future", Mnuchin said.
"The U.S. action will not help the solution of the problem as well as the mutual trust and cooperation with China", Hua said. The Trump administration is still hoping China will pressure Pyongyang.
"No Chinese banks were targeted, but that's the next level".
The sanctions also hit those who help individuals previously penalized for involvement in North Korea's weapons program and assist the country in sending workers overseas.
Richard Nephew of Columbia University said it appeared the U.S. government was "exploring what the tolerance is to the use of secondary sanctions".