Tonnes of gold are smuggled from the Democratic Republic of Congo as the production of the precious metal continues to be underreported, a United Nations report has found.

The report notes that gold worth billions of dollars is smuggled primarily through the DR Congo's eastern border and into the global supply chain.

North Kivu, South Kivu and Ituri provinces reported official production of just over 60kg of artisanal gold in 2019, yet exported a total of just over 73kg, the UN Group of Experts on the DR Congo found in its annual report seen by Reuters.

The group estimated that at least 1.1 tonnes of gold were smuggled out of Ituri province alone in 2019. That would have earned the government up to $1.88 million in taxes had it been legally exported.

Across all gold-producing provinces the loss is likely much greater. Artisanal miners in DR Congo produce 15 to 22 tonnes of gold a year, Germany's Federal Institute for Geosciences and Natural Resources has estimated.

"The country remained one of the Great Lakes region's largest artisanal gold producers, and yet one of its smallest official exporters," the Group of Experts wrote.

Trade in the precious metal has fueled regional wars, funded rebel fighters and led to UN sanctions on traders involved in a bid to staunch the flow.

The DR Congo government is yet to comment on the UN findings.