UN refugee agency chief Antonio Guterres on Friday urged more international help for thousands of Somalis devastated by a harsh drought, calling their plight the worst humanitarian tragedy.

Thousands of Somalis have fled into neighbouring Kenya and Ethiopia in recent weeks and many have died of starvation while fleeing due to one of the region's worst drought in decades.

"My main objective is to appeal to the international community to engage more actively in support of the Somali population that is suffering so much," Guterres said after visiting a camp hosting Somalis who fled into in Ethiopia.

"I have no doubt that if there is a population that is today suffering the worst humanitarian tragedy it is the Somalian population."

The UN High Commissioner for Refugees spokeswoman Melissa Fleming said in Geneva that many of the Somalis fleeing their country had died on the way, but could not give figures.

"Many people are dying en route from what we hear," she said.

Guterres said hunger and disease had claimed the lives of children as their families fled to seek relief in Ethiopia.

"I listened to mothers telling us that theyve lost their children on the way. Doctors said that they have no hope to rescue some of their patients because they are already condemned because they came too late to safety."

"Ive seen children dramatically impacted by malnourishment and disease. (It) is indeed something that breaks your heart," said Guterres.

Somalia has been the worst affected country in the drought-hit Horn of Africa region owing to the persistent violence since a civil war erupted there two decades ago.

About 1,700 Somalis are arriving daily in southeast Ethiopia, while in neighbouring Kenya about 1,400 each day reach the overcrowded Dadaab refugee camp, according to the UN refugee agency.

The European Union on Wednesday announced it would provide 5.67 million euros to help millions of people in the Horn of Africa affected by the drought.

The aid brought to almost 70 million euros the bloc's contribution to assistance for the millions of drought victims in parts of Ethiopia, Kenya, Somalia and Djibouti.

Somalia's Al-Qaeda-inspired Shebab rebels who two years ago banned foreign aid groups in areas under their control appealed for help and pledged to allow aid through to the population in their fiefdoms.

"If that can happen it would be very much welcome," Guterres told reporters in Addis Ababa.

"If access can be granted and people can be supported wherever they are that of course is a very important thing."

Guterres was in Ethiopia to assess the effect of the drought. On Saturday he will visit Kenya.

The UN's World Food Programme said it now expected 10 million people in the region to need food aid, revising upwards its six million figure given on Tuesday.

"This is extremely worrying. This is across the whole Horn. This is also affecting ... Kenyans, Ethiopians, Somalis," said Emilia Casella, spokeswoman for the UN food agency.