The experts' findings were first reported in early February by AFP and other news outlets who were given access to the document.

As revealed last month, North Korea has flouted sanctions by: continuing to export coal, iron, steel and other banned commodities; using ships with false flags of convenience; carrying out goods transfers at sea; and using fraudulent documents to mask coal shipments.

The Security Council last year adopted a series of resolutions to tighten and expand exports bans aimed at cutting off revenue to North Korea's military programs.

The United States led the push for tough economic sanctions after North Korea's sixth nuclear test and a series of ballistic missile launches that raised fears that the US mainland could soon be within reach.

Seven ships have been barred from ports worldwide for violating UN sanctions with coal and petroleum transfers, but the experts said much more must be done to confront "these rampant illicit activities."

The report is available at documents.un.org, by using the system number S/2018/171.