Aug. 10 (UPI) -- Three South Korean companies illegally imported North Korean coal and pig iron in 2017, violating international sanctions adopted in August of last year.
Shipments of North Korean coal into South Korea were smuggled into the country after the products were transshipped at a Russian port, according to South Korea's Customs Office on Friday, Yonhap reported.
Exports of North Korean coal, iron ore and other resources are banned under United Nations Security Council sanctions Resolution 2371.
The commodities are worth about $5.86 million, and shipments arrived in the South between April and October.
The firms imported the coal as "Russian products," according to the Korea Herald.
The companies have been referred to South Korea's prosecution, the customs office said.
Shipments of the commodities arrived in the South seven times.
South Korea's political opposition is demanding an explanation.
"The issue guarantees a parliamentary investigation as it can severely hurt national interests," said Kim Sung-tae of the Liberty Korea Party. "This is a grave diplomatic issue that cannot be neglected. We need to reveal who might have violated U.N. sanctions resolutions or whether the government was aware of [the entry of suspected ships]."
A panel of experts under the United Nations' North Korea sanctions committee had informed the Seoul government of the transfer of North Korean coal that occurred in October.