Coal from North Korea was shipped to the South on two occasions in 2017, according to an annual United Nations sanctions committee report.
The UN Security Council adopted a resolution last year banning exports of coal from the North along with other minerals.
U.S. broadcaster Voice of America cited the committee's report as it revealed the shipments arrived at the South Korean ports of Incheon and Pohang in October of last year.
The coal was apparently transported between July and September to Russia initially before being moved to the South on a pair of vessels registered in Sierra Leone and Panama respectively.
The report claimed that the Pohang delivery alone was valued around US$325,000.
Seoul and Washington remain officially committed to sanctions aimed at curbing Pyongyang's development of nuclear weapons, but some critics have suggested the current governments of both South Korea and the U.S. have given too much ground without North Korea fulfilling its recent promise to denuclearize.
By Alex Jensen in Seoul