The situation now is said to be worse than the crisis in 2003
The United Nations Children's Fund (Unicef) has appealed for extra resources to help thousands of severely malnourished children in Ethiopia.
The organisation says more than 126,000 children could be affected.
The World Food Programme says nearly 3m Ethiopians will need emergency food aid this year because of late rains and the high cost of food.
A BBC correspondent who visited a feeding centre says she saw a child whose arm was as thin as a man's thumb.
Some aid agencies running food and medical units say they are being overwhelmed with cases.
Consecutive failed rainy seasons, increases in food prices and a lack of resources for prevention and response mechanisms are all contributing factors in the drought-prone districts of Ethiopia, Unicef says.
Their bodies are almost consuming itself , they don't have any appetite
Indrias Getachew Unicef
It says the situation is the worst since the major humanitarian crisis of 2003, and is rapidly deteriorating.
The organisation says $50m (£25m) is urgently required for health, nutrition and water and sanitation.
"We had nothing to eat after the corn crop failed," said Dureti Degefi, one of the mothers at a feeding centre in Ethiopia's Siraro District. "My stomach is hungry. And my baby is sick. We need help."
Unicef's deputy representative in Ethiopia, Viviane Van Steirteghem non-governmental organisations were working in 55 districts and, with the government, managing to provide for about 50% of the cases.
"But there is a big capacity gap to take care of the remaining children," she said.
"A child with severe malnutrition is in immediate danger of death."
Children are treated at a feeding centre in Shashamina
The BBC's Elizabeth Blunt visited a centre for malnourished children at Bisidimo hospital not far from the eastern town of Harar.
Showing her around the centre and the queues of children, Unicef's Indrias Getachew told her:
''These children come in with severe malnutrition, some of them are oedemic, their bodies are almost consuming itself , they don't have any appetite."
Our correspondent says the country has not even reached the normal hungry season yet. The next harvest will not be until August or September.
She adds that the numbers of children who need help before then could be very large, stretching Ethiopia's ability to cope and the generosity of donors to supply the food that these very fragile children need.
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