South Korea is preparing to report its investigation results on alleged illegal North Korean coal shipments to the United Nations Security Council next week at the earliest possible date.

Seoul's customs office announced its probe results on Friday, which says that three South Korean firms imported North Korean coal and pig iron from Russia on seven occasions between April and October last year in an apparent violation of a UN sanctions resolution.

A government official said Saturday that the government is translating the probe results and making related preparations to send its report to the UN Security Council.

The official said that the government plans to report the results as soon as possible, adding it will report them next week if possible.

The official added the report will also include a list of four cargo ships used for the banned activities, including a Belize-flagged ship, the Jin Long.