An anti-graft pressure group has called for a probe into the alleged purchase of a luxury US beach house by the son of Equatorial Guinea's president.
President Obiang has ruled his country since 1979
Teodoro Nguema Obiang bought a $35m house in California's exclusive Malibu area in February, Global Witness says.
His pay as a minister is $60,000 a year. The country was named recently as one of the world's most corrupt.
Africa's third-biggest oil producer earns $3bn a year but most people live on just $1 a day.
Global Witness said it obtained the information on the purchase of the 16-acre property from public records available in Los Angeles.
The president's son bought the mansion in the name of Sweetwater Malibu, LLC, a company he wholly owns and manages, Global Witness said.
The lobby group which campaigns against the use of resources like oil being used to fund abuses, conflict and corruption has called on the United States government to investigate the source of the wealth.
"This could be a test case for this initiative," campaigner Sarah Wykes told Reuters news agency.
"Where is this money coming from?" she asked.
An adviser to Equatorial Guinea's government, who wanted to remain anonymous, said Mr Obiang was a businessman with independent sources of income before he became a cabinet minister, AP news agency reports.
Mr Obiang has not responded himself.
Last year, a South African court seized two luxury homes registered in his name in Cape Town.
In 2004, a US Senate investigation discovered that Equatorial Guinea's president, Teodoro Obiang Nguema Mbasogo, and members of his family were the signatories to accounts at Riggs Bank in the US which had received millions of dollars in revenues from the central African country's oil wells.