The United Nations on Monday declared a sixth region of Somalia to be a famine zone, and warned that the crisis is expected to spread further in the coming months.
"In total, 4 million people are in crisis in Somalia, with 750,000 people at risk of death in the coming four months in the absence of adequate response," the U.N. Somalia Food Security Nutrition Analysis Unit (FSNAU) said in a statement.
FSNAU said the prevalence of acute malnutrition and the rate of crude mortality in the Bay region of southern Somalia, which includes the town of Baidoa, have surpassed famine thresholds.
"Assuming current levels of response continue, famine is expected to spread further over the coming four months," the statement said.
The Bay region is a stronghold of al Qaeda-linked rebel group al-Shabab, which has blocked aid agencies from delivering assistance in areas under its control.
The U.N. has already declared famine in the southern Bakool and Lower Shabelle regions, as well as the Somali capital Mogadishu and two rural districts of the Middle Shabelle region.
In total, half of southern Somalia is now suffering from famine, the Associated Press says.
"An additional 50,000 people in cropping areas of Gedo and Juba and pastoral areas of Bakool face famine-level food deficits," the FSNAU statement added.
"Tens of thousands of people have already died, over half of whom are children."
To be classified as a famine, more than 30 percent of children in an area must be suffering from acute malnutrition, two adults or four children per 10,000 people must be dying of hunger each day, and the population must have access to below 2,100 kilocalories of food per day.
It is the first time in 19 years that war-torn Somalia, which has been without a central government since 1991, has experienced famine.
Al-Shabab fighters pulled out of much of Mogadishu last month, but still control large swathes of southern Somalia, the worst-hit region by the drought and famine.
The U.N. estimates that 12.4 million people across the drought-stricken Horn of Africa region, including parts of Kenya, Ethiopia, Djibouti and Uganda, are facing severe food shortages and are in desperate need of aid.