A new World Bank report says sub-Saharan Africa is poised for faster economic growth after a strong performance last year.

In a report published Wednesday, the World Bank says the region's economy grew at a 4.9 percent annual rate in 2011, making it one of the world's fastest-growing developing regions.

It says growth has been helped by a rising middle class and increased foreign investment, which has been encouraged by rising prices for the region's commodity exports.

However, the report's authors say growth is threatened by food shortages in West Africa's Sahel region. Poor rainfall and conflict there have left at least 13 million people vulnerable.

World Bank experts also warn that the high cost of fuel subsidies is hurting government budgets in many nations.