(CNN) -- They have become refugees so they can eat, sometimes walking for days to reach a camp where they might find something to fill their aching bellies. After the head of the United Nations' refugee agency got a firsthand look at the suffering people of East Africa, he said Friday his heart was broken.
The agency put out an urgent plea for $136 million in international donations to address life-saving needs.
"Refugee children are dying and their mothers, reduced to walking skeletons, face the unbearable choice of which child to save first," said the U.N. High Commissioner for Refugees, Antonio Guterres, who visited a refugee camp in southeast Ethiopia.
The refugees are not victims of a sudden disaster like an earthquake or tsunami, but of a crisis slow in the making and as yet largely off the global radar.
Two consecutive poor rainy seasons over the past year have dried up pastoral areas in the Horn of Africa, where the drought is exacerbated by already sky-high food prices, restricted humanitarian access and conflict.
About 10 million people in Somalia, Ethiopia and Kenya are now at risk of starvation as the region faces the worst drought in 60 years, according to the United Nations.
"2011 has been the year of all crises, but I think that in Somalia we can find the worst humanitarian disaster of this year," Guterres said.
"Our heart is broken when we see mothers telling us that after having walked for days to reach safety, they have lost their children along the way, (and) to see children dying and then doctors not being able to help because it is too late," he said.
In a parched and remote area of southeastern Ethiopia near the Somali border, away from the world's watch, Guterres witnessed a deepening struggle to keep desperate people alive.
A new refugee camp in Kobe was opened just weeks ago. Already it is teeming with people and nearing its 20,000-person capacity.
The new arrivals are mostly from war-torn Somalia, a nation wracked by civil war for the past two decades.
The U.N. refugee agency said the flood of Somalis -- 55,000 people entered Kenya and Ethiopia in June alone -- could overwhelm the ability of humanitarian agencies to help them. About 1,700 people are arriving every day.
"Humanitarian efforts to help newly arriving Somali refugees in southeast Ethiopia are at risk of being overwhelmed without a more rapid and robust international response to the drought and displacement crisis in the Horn of Africa," said Melissa Fleming, spokeswoman for the agency.
"Urgent help is needed," she said.
Malnutrition rates are alarmingly high among the most recent arrivals, Fleming said. At least 50 percent of children do not have adequate food.
Somalis are also pouring into the already full Dadaab refugee complex in Kenya, the largest in the world, with more than 350,000 people and counting. About 80 percent of them, Fleming said, are women and children.
About one quarter of Somalia's 7.5 million people are either internally displaced or have fled the country as refugees, Fleming said.
Natural disaster has met man-made violence in Somalia, number one on a global list of failed states. The people caught in the middle are struggling to stay alive.
CNN's Moni Basu contributed to this report.