Around 5,000 Somalis have fled in scorching temperatures to refugee camps in neighboring Kenya and Ethiopia.

“Nearly half of the Somali population - 3.7 million people - are now in crisis, of whom an estimated 2.8 million people are in the south,” said Mark Bowden, the UN humanitarian coordinator for Somalia.

The United Nations declared a famine in southern Bakool and Lower Shabelle.

Soon after the announcement early Wednesday, the US secretary of state, Hillary Clinton, announced US$28 million in additional funding for Somalis and Somali refugees in Kenya.

“We have already responded with over US$431 million in food and non-food emergency assistance this year alone,” Clinton said in a statement. “But it is not enough - the need is only expected to increase and more must be done by the United States and the international community.”

Severe drought, crop failure, livestock deaths, soaring food prices and conflict have forced millions of people in several east Africa nations to flee their homes.

In all, about 11 million people are affected in Kenya, Ethiopia, Djibouti, Uganda and Somalia, with the latter mostly affected, according to the United Nations.

Most of the Somalis have fled to the Dadaab refugee camp in Kenya, which was originally built for 90,000 people and is now home to nearly 400,000.

The south is home to about 80% of the nation's malnourished children, the United Nations Children's Fund said.

Aid groups declare a famine based on data from the food security and nutrition analysis unit, which uses factors such as food prices, weather conditions and malnutrition rates.

For a famine to be declared, at least 20% of households must be facing extreme food shortages with limited ability to cope, the UN said in a statement.