Angola's government announced Wednesday the creation of a sovereign wealth fund that will invest profits from oil sales in businesses in an effort to diversify the country's economy and spread prosperity beyond the small elite that has benefited from Angola's outsize economic growth.

With start-up capital of $5 billion, the fund will be the second richest in sub-Saharan Africa after Botswana's. There, a portion of the proceeds of the diamond industry have been socked away for almost two decades.

The Angolan fund, which will focus on investments in Africa's booming hotel industry and large infrastructure projects, seeks to wean the economy from oil, a finite resource, to a more diversified and sustainable base, said José Filomeno de Sousa dos Santos, a son of President José Eduardo dos Santos, and a member of the fund's board.

"The economy is very one sided and very correlated to the volatility of oil prices," the younger Mr. dos Santos said in an interview. "The aim is to create wealth for future generations."

Angola is sub-Saharan Africa's second-biggest oil producer after Nigeria, with an output of about 1.8 million barrels of crude a day. Oil accounts for nearly all of the country's export earnings and almost half of its gross domestic product.

Many resource-rich countries have created funds that invest broadly to hedge against fluctuating commodity prices, the biggest being oil-rich Norway's government pension fund. Some American states, like Alaska and Wyoming, have funds that either directly pay citizens a dividend of mineral wealth or invest it on their behalf.

Oil wealth has transformed Angola's seaside capital, Luanda, building a glittering skyline and jamming its streets with expensive sport utility vehicles. After decades of civil war fueled in part by the country's rich diamond deposits, Angola has been at peace for the last decade, and it has prospered mightily.

Oil wealth has also made Angola one of the world's most unequal nations, and poverty remains rampant, especially in rural areas. Furthermore, the government seems to subsist from barrel to barrel, with little stashed away for a rainy day. When oil prices dropped amid the financial crisis in 2008, Angola was forced to ask the International Monetary Fund for help.

But the government's bookkeeping is notoriously opaque. The monetary fund said this year that $32 billion spent by the state oil company, Sonangol, over several years, could not be accounted for. Anticorruption activists have long accused top government officials of enriching themselves while leaving the masses to struggle without clean water, decent housing and affordable health care.

Mr. dos Santos said in the interview that the fund would follow a clearly delineated investment strategy and open its books to annual independent audits.

"We are committed to transparency," he said.

The fund's elegant offices, a few floors down from the oil industry services company Halliburton, are decorated with raw silk wallpaper, designer furniture and black lacquer fittings.