US President Barack Obama urged Africans on Saturday to ask more questions about lop-sided deals with some foreign investors, while dismissing talk of a Chinese and US scramble for influence on the continent.

During a landmark visit to the continent of his father's birth, Obama said he welcomed renewed interest from larger emerging markets.

"I actually welcome the attention that Africa is receiving from countries like China and Brazil and India and Turkey."

But he urged African nations to make sure trade was not a one-way street.

"When we look at what other countries are doing in Africa, I think our only advice is make sure it's a good deal for Africa."

"Somebody says they want to come build something here: Are they hiring African workers? Somebody says that we want to help you develop your natural resources: How much of the money is staying in Africa?"

Obama, in South Africa on the second-leg of a three-nation Africa tour, said that too often foreign investment did not benefit locals and actually encouraged the type of corruption and resource-stripping that guts economies.

"I do think that it's important for Africans to make sure that these interactions are good for Africa."

"There has been a long history of extracting resources from Africa, you take raw materials, you send them to someplace else where they get used processed, sometimes sold back to Africa.

"The profits stay there the jobs stay there and not much stays in Africa."

Obama offered up the United States as a more equitable partner which wanted African economies to grow into consumer powerhouses.

Strong economies would mean the United States would get "somebody to trade with, to sell iPods to, airplanes, all kinds of good stuff."

"Frankly we don't need energy from Africa," he said pointing to developments in natural gas, clean energy and oil shale at home.

Amid a raft of Chinese investment in Africa, which topped $200 billion last year, US businesses have expressed concern that Africa is a diplomatic blind spot for their government.

In March, China's new President Xi Jinping visited Africa, as well as Russia, on his first foreign trip, signing a raft of business and energy deals signalling Beijing's intent to deepen ties further.