The United Nations has declared a famine in two areas of southern Somalia, amid the worst drought to hit the country in more than 50 years.

Speaking in Nairobi, U.N. spokesman Mark Bowden said famine exists in the Nakool and Lower Shabelle regions.

U.S. Secretary of State Hillary Clinton released a statement expressing deep concern about the humanitarian emergency in the Horn of Africa and Wednesday's announcement by the United Nations about Somalia.

Secretary Clinton said the U.S. will provide an additional $28 million in aid to the more than $431 million in food and non-food emergency aid assistance.

While touring a displaced-persons camp in the capital, Mogadishu, on Tuesday, Somalia's President Sheikh Sharif Sheikh Ahmed said food has become so scarce that there is “in fact a famine” in his country.

The U.N. refugee agency, UNHCR, has said it needs more security assurances from Somali insurgents in order to provide the massive level of aid needed in the country.

Militant group al-Shabab says it welcomes the return of relief organizations, after barring them from its strongholds in central and south Somalia more than a year ago.

But UNHCR spokesman Adrian Edwards told VOA that the agency must still keep a “low profile” and work through partners to avoid being targeted by al-Shabab and other armed groups.

The United States said Tuesday it is assessing whether al-Shabab is following through on its promise to let aid groups operate freely in Somalia.

The top U.S. diplomat to Africa, Johnnie Carson, said al-Shabab's policies have been “wreaking havoc” on Somalis.

The country has been wracked with lawlessness and deadly violence for years. Al-Shabab is fighting to overthrow the U.N.-backed Somali government and set up a strict Islamic state.