The U.N. World Food Program is set to begin its emergency airlift of food to the drought-stricken Horn of Africa on Wednesday.

WFP director Josette Sheeran told VOA the first flights will head to Somalia's capital, Mogadishu. Additional planes are expected to carry food to eastern Ethiopia and northern Kenya, near the Somali border.

On Wednesday the U.N. plans to hold a donor's conference in the Kenyan capital Nairobi, with the goal of raising up to $1.6 billion to combat the famine over the next 12 months.

U.N. Secretary General Ban Ki-moon spoke Tuesday with leaders from four Persian Gulf states, urging them to pledge more aid to combat the “deteriorating humanitarian crisis.” Sheeran said that Saudi King Abdullah recently pledged an additional $50 million in food aid.

U.N. officials have said more than 11 million people are in need of emergency aid. Sheeran said that in Somalia, about one-third of the population is facing starvation — and that people tell of having to leave dying family members behind as they walk toward refugee and displaced-person camps for help.

On Tuesday, the U.N. refugee agency said 100,000 Somalis have arrived at Mogadishu-area camps in the past two months, and continue to come at a rate of 1,000 per day.

Thousands more are streaming across the border to camps in Kenya and Ethiopia. On Wednesday, the U.N. Children's Fund said it aims to vaccinate over 300,000 children in Kenya to prevent new outbreaks of disease.

U.N. access to southern Somalia — where the U.N. formally declared a famine last week — has been hampered by the militant Islamist group al-Shabab. The group controls large sections of the region and has denied that a famine is taking place, dismissing international assistance as political interference.