More than two million Somalis could die of starvation by the end of the summer if international aid is not sent quickly to the drought-stricken African country, according to a UN emergency relief co-ordinator.

UN undersecretary-general Mark Lowcock says about $US700 million ($A1000 million) is needed after a rainless season that has killed livestock and crops.

He said the UN's Central Emergency Response Fund has allocated $US45m ($A64m) to cover food shortages, water and daily necessities in Somalia as well as parts of Kenya and Ethiopia affected by droughts.

Of a Somali population of 15 million people, more than three million are struggling to meet minimum food requirements, he said, and the shortages are about 40 per cent worse than during the winter.

"What was forecast to be an average rainy season in Somalia is now one of the driest on record in over 35 years," he said.

"Communities that were already vulnerable due to past droughts are again facing severe hunger and water scarcity and are at risk from deadly communicable diseases."

The UN aid complements efforts by governments of the three countries to assist their people, especially those with disabilities or who are internally displaced.

Mr Lowcock, who heads the UN Office for Humanitarian Affairs, said that in past decades droughts came about every half dozen years, but recently they have hit every two or three years.

"There's not really any question in my mind that these more frequent droughts are related to global warming and climate change. So the only middle and longer-term response is to look at alternative livelihoods - a different way to make a living."