CARACAS - Venezuela sent gold to Mali in 2020 via Russian-owned planes to exchange for euros and US dollars that President Nicolas Maduro's government used to remain afloat despite US sanctions, an opposition representative said on Wednesday.

Julio Borges, designated by opposition leader Juan Guaido as his chief overseas envoy, told reporters that the gold was refined in Mali and then resold primarily in the United Arab Emirates (UAE) to allow for Maduro's administration to obtain the equivalent of at least $1-billion in euros in particular.

The United States, which accuses Maduro of rigging his 2018 re-election, imposed sanctions on Venezuela's state oil company in early 2019 in a bid to pressure Maduro to resign. His socialist government has increasingly turned to the sale of monetary gold as a source of income, with central bank reserves dropping to a 50-year low.

"We are requesting that US and European authorities make their system for dismantling these types of organized crime groups more sophisticated," Borges said, adding that the opposition had been tracking the Venezuelan gold trade for the past year, culminating in the report presented Wednesday.

Borges said that Noor Capital, an Emirati company that in early 2019 said it had bought three tonnes of gold from Venezuela's central bank but would refrain from further transactions until Venezuela's situation stabilized, had been involved in the 2020 transactions.

Noor Capital did not immediately respond to a request for comment on Wednesday. Noor had said in January 2019 that its purchases of Venezuelan gold were in accordance with "international standards and laws in place" as of Jan. 21 of that year.

Reuters could not independently verify Borges' assertions. One person close to the Venezuelan government said that much of the gold leaving the country was destined for the UAE after two stops, but did not provide further details.

Neither Venezuela's central bank nor the government's information ministry immediately responded to requests for comment.

The UAE and Mali governments also did not immediately respond to requests for comment.

The UAE, one of the world's largest gold hubs, has responded to previous criticisms of opacity in its bullion trade by pledging to develop "increasingly robust mechanisms to address the challenges brought about by financial crime."

Washington, which has put sanctions on the South American country's gold exports, said that Maduro continued to sell gold to fund itself.

"Since 2016, Maduro has actively encouraged, supported, and facilitated the illegal mining, distribution, and sale of gold by his inner circle, funding repression, treating the country's natural resources as his own, and devastating fragile ecosystems," a US State Department spokesperson said.

Maduro, who retains the support of the Venezuelan military and allies including Russia, China and Cuba, argues Guaido is a US puppet seeking to oust him in a coup.