A widespread famine is affecting more than 12 million people across the Horn of Africa.

International aid agencies in Ethiopia, Somalia, Djibouti and Kenya say years of low rainfall have lead to a severe drought, wiping out livestock and damaging crops.

Other areas at risk are Sudan, Uganda, Eritrea and Tanzania. Aid workers say that it is difficult to assess the extent of the crisis because many of the areas are hard to access.

An Oxfam official, Nick Roseveare, told the BBC that the situation is especially bad in south-eastern Ethiopia, where children and elderly people are already reported to be dying.

"At the moment it is still very dry and it should have been raining for some time. If the rains do come they are very likely to be too late and insufficient," he said.

Mr Roseveare said up to one million tonnes of food would be required over the next year to overcome the crisis.

Pledges not enough

He said although donors had pledged assistance, many have yet to fulfil those promises.

"Donors do need to act now to turn their pledges into a practical commitment that is on the high seas and that is on its way to Ethiopia."

In northern Kenya, aid workers say refugees fleeing Sudan and Somalia are draining already scarce food resources.

The Ethiopian Government has already requested more than 800,000 tonnes of emergency food and the United States relief arm, USAID, have pledged about half of that.

A US official visiting Ethiopia recently concluded that the situation was deteriorating so rapidly that immediate aid was needed.

He announced an initial airlift of 20 tonnes of blended foods, milk and high energy biscuits for eastern Ethiopia.

He also called for help from the European Union and Japan.

Last month the United Nations World Food Programme approved $137m in emergency aid.