The US Treasury sanctioned Belgian gold trader Alain Goetz and his African Gold Refinery, one of the continent’s biggest processors of the metal, for allegedly contributing to conflict in the Democratic Republic of Congo.

Goetz and Uganda-based AGR are key players in Congo’s illicit gold trade, which is worth hundreds of millions of dollars each year and is the largest source of revenue for armed groups in the country, the Treasury said Thursday in an emailed statement. Goetz, AGR, and eight other linked companies will have their US-based assets blocked under the sanctions, it said.

“Alain Goetz and his network have contributed to armed conflict by receiving DRC gold without questioning its origin,” Under Secretary of the Treasury for Terrorism and Financial Intelligence Brian Nelson said in the statement. “Treasury has been very clear: global gold markets, at every step of the supply chain, must engage in responsible sourcing and conduct supply-chain due diligence.”

Goetz was sanctioned under two executive orders signed during the Bush and Obama administrations that target “persons threatening the peace, security, or stability of the DRC and the surrounding region.”

Goetz didn’t immediately provide comment when reached by text message on Friday. AGR’s website no longer operates and the company’s phone was off when called for comment.

Conflict in mineral-rich eastern Congo began in the mid-1990s, when the civil war and genocide in neighboring Rwanda spread over the border, igniting a war that eventually enveloped more than a half-dozen African nations. Despite a 2003 peace agreement, fighting persists in eastern Congo. More than 100 armed groups are active in the region, which has almost 5 million displaced people, the largest number in Africa, according to the United Nations.

In 2018, AGR refined about half a billion dollars worth of gold, according to the Treasury statement. In a 2020 speech, Ugandan President Yoweri Museveni said the refinery was earning more than $1.25-billion per year.

“The sanctions are of concern to Uganda,” Minister of State for Foreign Affairs Henry Okello Oryemsaid by phone. “We are going to study the clauses based on by the US and we shall respond to the matter.”

Record gold prices have seen an explosion in African gold exports, Bloomberg News reported last year. Most of the gold ends up in the United Arab Emirates, where three of Goetz’s sanctioned companies are based.

The most recent estimates of gold exports from Uganda and Rwanda show the combined value of the trade may be almost $3-billion annually, an amount that doesn’t reflect what’s mined in the two countries. The UN group of experts monitoring the links between conflict and natural resource extraction in Congo says that a large share of that gold is Congolese. The group has named Goetz and AGR in several of their annual reports.