By DEVON MAYLIE

JOHANNESBURG—Yum Brands Inc. plans to expand its KFC fast-food chain into seven more countries across Africa in 2012 and add 100 stores on the continent, as it seeks to tap into a rising middle class and strong economic growth, its general manager for Africa operations said Tuesday.

The 2012 KFC expansion will equate to a roughly 600 million rand ($74 million) investment. The Africa division is also looking at bringing Pizza Hut, another Yum brand, to South Africa this year or next, Keith Warren said in an interview.

In 2010, the Louisville, Ky., restaurant company said it expected to double the number of KFC outlets in Africa to 1,200 by 2014. That goal is still intact despite the global economic uncertainty, Mr. Warren said, adding that the rise in commodity prices and currency fluctuations will push up costs and food prices.

In 2011, KFC outlets were opened in Zambia, Ghana and Kenya. This year stores are already being built in Angola and Malawi, with Tanzania, Uganda, Angola, Zimbabwe, Congo and Madagascar to follow, Mr. Warren said.

Retailers and food companies are pushing to expand across Africa, driven by figures such as those from the African Development Bank, which estimates that Africa’s middle class—those earning between $4 and $20 a day—will increase to 1.1 billion people by 2060 and account for 42% of the continent’s population.

In addition, Africa’s economic growth is expected to outpace more developed regions. The International Monetary Fund forecast economic growth in sub-Saharan Africa to be nearly 5.8% this year, beating the forecast global average of 4% this year.

Mr. Warren said the main challenges to more rapid expansion across Africa are restrictions on free trade in some countries and also political instability.