A confidential report prepared by independent United Nations monitors and seen by Reuters on Friday also states North Korea supplied weapons-including ballistic missile systems-to Syria and Myanmar. The coal had reportedly been shipped worldwide to countries such as China, South Korea, Russia, Malaysia and Vietnam.
It said "there was proof that Pyongyang was helping Syria to develop chemical weapons and providing ballistic missiles to Myanmar".
The same inspectors added that multinational oil companies, which remained nameless in the report, were also subject to investigation for their participation in the supply chain of petroleum products moved to North Korea, Reuters reported.
A 213-page report obtained by the news service accuses North Korea of flouting bans on exports of North Korean coal, iron, lead, textiles and seafood, the news service reports, as well as sanctions meant to hamper the country's ballistic weapons program.
North Korean leader Kim Jong Un watches the launching of the medium-to-long range strategic ballistic rocket at an unspecified location on September 16, 2017.
Those documents listing countries like Russian Federation and China as the origin of the coal, instead of North Korea.
The confidential report to a U.N. Security Council sanctions committee also referenced information that the reclusive country provided ballistic missile systems to Myanmar.
The report says the North used trans-shipment through third countries and fraudulent documentation to obscure the origin of the coal.
Under a 2016 resolution, the UN Security Council capped coal exports and required countries to report any imports of North Korean coal to the council sanctions committee.
The report said "if confirmed, it would constitute the resolution's violation".
The panel revealed that between 2012 and 2017, there had been over 40 North Korean shipments to companies acting for the research centre overseeing Syria's chemical weapons programme.
The UN monitors "also investigated cases of ship-to-ship transfers of petroleum products in violation (of UN sanctions). and found that the network behind these vessels is primarily based in Taiwan province of China".
Syria denied the presence of North Korean technicians in its territory, claiming that the only experts it was hosting from the country were involved in sport. It then banned all exports of coal by North Korea on August 5.
It pointed out that Chinese food, fruit and household products were still being sold in North Korea.