The World Food Program says it expects 10 million people will be in need of food aid, as the worst drought in decades continues to devastate the Horn of Africa.

The drought is centered in the triangle where the nations of Somalia, Kenya and Ethiopia meet. It has produced a mass migration of starving citizens and created the largest refugee camp in the world.

Dadaab, in northeastern Kenya, built for 90,000, currently holds more than 380,000 Somalis, and hundreds more refugees pour in daily. The camp was visited on Sunday by Antonio Guterres, the head of the U.N. refugee agency. He later told reporters that “massive support” is needed to combat the “worst humanitarian disaster” in the world.

International agencies face difficulties in providing aid to those who remain in Somalia, which lacks a functioning government and whose territory is dominated by the Islamist rebel group, al-Shabab.