Oxfam has launched an emergency appeal for £9.5m ($15m) to reach millions of people threatened by hunger in Ethiopia and other East African countries.
The UK-based agency says thousands of animals have already died because of a drought which is the worst in 10 years.
Warning signs indicate that the lives and livelihoods of 23 million people are threatened - twice as many as the last serious crisis in 2006.
Seven countries are affected, with half of those threatened living in Ethiopia.
However, Ethiopian officials say that fewer people will actually need food aid this year than in 2008.
The government says it is confident it has done everything it can to feed its hungry people.
Other worst affected countries are Kenya, Somalia and Uganda, with Sudan, Djibouti and Tanzania also hit hard.
Oxfam says many infants have fallen ill and the elderly - who traditionally are the last to get food and water - are the worst hit.
"My body has had so little over the last few months it has given up [taking solid food]," Muya Emaniman, an elderly woman from Kanukarudio, in the Turkana region of northern Kenya, told the Press Association.
Livestock - an important source of income - have been dying
"Usually if the rains fail, we have built up a reserve of food we can fall back on. But this time it is worse than that because they have failed again and again," she said. "We have nothing left."
Mother-of-five Ajikon Lonok, said her children were getting ill with diarrhoea.
"Taking water here is no good because it is contaminated, but it is all we have unless we walk all day," she told PA from her village near Kokuro.
Conflict, climate change and population growth have all played their part in worsening the effect of a drought this year which comes after four years of bad harvests, says the BBC's international development correspondent, David Loyn.
He says if the rains do come next month, the El Nino effect might turn them into uncontrolled deluges - causing more death rather than helping to grow crops.
A spokesman for the UK Department for International Development says that they too are gravely concerned and ready to provide emergency supplies as necessary.
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