The United Nations says famine has spread to three new parts of southern Somalia, including areas in the capital, Mogadishu.

A statement Wednesday said famine conditions are present in two districts of the Middle Shabelle region, the Afgoye corridor displaced persons settlement, and in the Mogadishu displaced persons community.

The statement says rates of acute malnutrition and mortality have passed famine thresholds in all three areas.

The U.N. declared Somalia's Bakool and Lower Shabelle regions to be famine zones last month.

Wednesday's statement says a humanitarian emergency persists across all of southern Somalia, and says “tens of thousands of excess deaths have already occurred.”

It says the current aid response is inadequate because of problems with funding, logistics and access. The U.N. predicts that famine will spread across the entire south in coming weeks and will persist until December.

Somalia is at the center of the worst drought to hit the Horn of Africa in 60 years. The United Nations says more than 12 million people in the region are in need of food aid.

Earlier Wednesday, the U.N. refugee agency said the number of Somali refugees in the Horn of Africa has climbed to more than 860,000, many of them forced out by the famine.

The agency says another 1.5 million Somalis are internally displaced, mostly in south-central Somalia.

On Tuesday, British relief agency Oxfam said governments and donors need to fulfill their pledges of aid more quickly.

International aid efforts have been hampered by the militant group al-Shabab, which controls much of southern and central Somalia.

The group, which is trying to overthrow the Somali government, has denied a famine is taking place and has tried to block aid workers from reaching starving Somalis.