ENTEBBE, Uganda—The government of Venezuelan President Nicolás Maduro is selling off his country’s gold reserves. Some of it has passed through a secretive operation in East Africa, a gambit that evades U.S. sanctions.

On two early-March flights, at least 7.4 tons of gold with a market value over $300 million moved from Venezuela to a refinery in Uganda, say officials in Venezuela and Uganda, a foreign diplomat and Venezuelan opposition lawmakers, who have concluded Mr. Maduro’s government exported the ingots.

The gold arrived on a Russian charter jetliner in two shipments at the international airport in Entebbe, says Ugandan national-police spokesman Fred Enanga. The accompanying paperwork identified the ingots, some with stamped labels partially scratched off, as Venezuelan central-bank property, says a senior Ugandan police officer who saw the bars and documents. Flight records show the trips originated in Caracas, Venezuela.

The shipments expose one link in a global underground economy many suspect is helping Mr. Maduro cling to power by bypassing the U.S.-dominated international finance system. Washington has recognized opposition leader Juan Guaidó as Venezuela’s legitimate president, slapped financial and other sanctions on Venezuelan officials and institutions, and threatened penalties for others doing business with the regime.

The standoff between the two leaders is reverberating beyond Venezuela, with some 50 countries joining the U.S. in backing Mr. Guaidó while others side with Mr. Maduro. What was once Latin America’s richest economy is starving, its oil sales have dwindled and citizens are suffering through dayslong power outages and shortages of basic goods.