(GIN) – Africa’s oil giants are tightening their belts as the sale price of “King Oil”, buffeted by cheaper fracked gas, solar and other renewables, hits new lows.

The promises of prosperity have faded in Ghana, Uganda, and Nigeria, among other oil producers.

Perhaps the saddest scenario can be found in Angola – whose capital Luanda was not long ago rated among the most expensive cities in the world, along with Zurich, London, Hong Kong, Sydney, Singapore and Tokyo. Yet 94% of the population in rural areas is categorized as poor.

“The oil boom offered a golden opportunity for self-enrichment,” observed Norimitsu Onishi of the New York Times. Under President José Eduardo dos Santos, his inner circle of family and allies amassed extraordinary wealth.

Isabel dos Santos, the president’s eldest daughter, became Africa’s first female billionaire, according to Forbes Magazine, which estimates her wealth at $3.3 billion.

Now, with lowered hopes for an oil recovery, Mr. dos Santos prepares to step down after 38 years in power. Meanwhile, the country’s building boom and the wealth of its ruling class are coming under greater scrutiny and in some cases prosecution for abusive excesses.

Last April, Brazilian construction giant Odebrecht SA was ordered to pay $2.6 billion in fines in a massive criminal corruption case that included bribing Angolan officials to approve building projects. The case was heard in a Brooklyn federal court.

A study by Angola’s Center for Studies and Scientific Research at the Catholic University, found that $28 billion from government budgets for the period 2002 to 2015 was unaccounted for. Up to 35 percent of the money spent on road construction alone has vanished, according to the center’s investigation.

During the same period, Angolan companies and individuals invested $189 billion overseas in often opaque transactions, the center found.

Former prime minister and ex-secretary general of the ruling party, Lopo do Nascimento, compared government spending to “opening a window and throwing out money.”

Currently, elections are scheduled for August, but the hand-picked candidate for presidency has run into trouble of his own. A Portuguese judge has ruled that Vice President Manuel Vicente must be prosecuted for corruption and money laundering, including bribing a magistrate when he headed the state-run oil company Sonangol.

Two of his legal and financial representatives in Portugal have also been charged. w/pix of Chinese construction site in Lubango, Angola