The United Nations refugee agency says drought and violence have now driven one-quarter of Somalia's 7.5 million people from their homes, either to internal camps or to refugee camps abroad.

The agency's estimate Tuesday comes as aid groups seek urgent help for Somalia, where the lack of rain has compounded chaos caused by years of civil conflict.

The refugee agency says it is especially disturbed by the high levels of malnutrition among the newest Somali refugees. It says more than half of Somali children arriving in Ethiopia are seriously malnourished, as are about 40 percent arriving in Kenya.

It says that tragically, many children are so weak when they arrive that they die within 24 hours despite emergency care and feeding.

The United Nations and international relief groups say persistent drought in the Horn of Africa has left up to 10 million needing food aid. The British groups Oxfam and Save the Children launched an emergency appeal this week.

The groups are also raising alarm about conditions at the Dadaab refugee camps in Kenya. The U.N. says the camps, originally built to hold 90,000 people, now hold more than 380,000.

The U.N. refugee agency reported a clash between residents and police near a food distribution point in Dadaab last Thursday. It called the incident “symptomatic” of the pressures at the overcrowded camps.