A sixth region of Somalia has been declared a famine area by the UN, which warns the situation will only worsen in the coming months.The number of people dying in the southern Bay region has now passed the threshold to be defined a famine, the UN says.It says tens of thousands of people have died after what is said to be East Africa's worst drought for 60 years.Some 12 million people across the region needs food aid, the UN says.Of these, four million are in Somalia and unless more aid arrives soon, some 750,000 could die in the country, the UN's Food Security and Nutrition Analysis Unit (FSNAU) says.Neighbouring Kenya, Ethiopia, Eritrea and Uganda have also been affected by the severe lack of rain.But 20 years of fighting and the lack of a national government mean that Somalia is by far the worst affected country.BBC East Africa correspondent Will Ross says it is still hard for humanitarian agencies to reach the population in areas controlled by the Islamist insurgent group al-Shabab.Some food aid is getting there but not on the scale that is needed, he says.The al-Qaeda-linked group controls much of southern Somalia - the worst hit part of the country.