The United Nations has begun delivering aid to areas of Somalia controlled by al-Qaida-linked militants — a testament to the severity of the drought devastating East Africa. 
 
 Al-Shabab two years ago had banned foreign aid in territories that it controls, feaing that aid agencies could host spies or promote an un-Islamic way of life. But in recent weeks, tens of thousands of Somalis have fled militant-controlled areas because of a lack of food. And al-Shabab said earlier this month that it wanted to negotiate aid agencies' return. 
 
 Rozanne Chorlton, the UNICEF representative for Somalia, told the BBC that al-Shabab had assured the agency it could operate freely. 
 
 "They gave assurances that our access for humanitarian purposes would be unhindered and that we would be able to reach the people who need support most," Chorlton told the BBC. 
 
 UNICEF on Thursday called the drought and refugee crisis "the most severe humanitarian emergency in the world." The international Red Cross signaled "great alarm" this week at the nutritional state of Somali children. 
 
 Fears of famine 
 
 On Wednesday, UNICEF made what appears to be the first outside aid drop by air to the al-Shabab-controlled town of Baidoa, flying in 5 metric tons of food, clean water equipment and medicine. Baidoa is about 125 miles northwest of Mogadishu, the capital. 
 
 The United States, the United Kindom and some other western nations have designated al-Shabab as a terrorist organization. It and its allies control much of southern Somalia and about half of Mogadishu. 
 
 theGrio: Drought raises regional tensions 
 
 UNICEF says that more than a half million Somali children face life-threatening conditions with long-lasting consequences for their physical and mental development. 
 
 Thousands of Somalis have been walking days and sometimes weeks to reach refugee camps, including the huge Dadaab complex in northeastern Kenya. 
 
 "More children have died of malnutrition in the first four months of this year than in the whole of last year," said Andrew Wander, a spokesman for Save the Children. 
 
 With a population of almost 400,000, Dadaab is beginning to resemble a city, with up to 1,500 new arrivals everyday, according to NBC News. Dadaab was originally built for 90,000 people; more than 382,000 are now here. 
 
 The U.N. expects at least 10 million people will need food aid, and a U.S. aid official said he believes the situation in Ethiopia is even worse than the government acknowledges. 
 
 The Ethiopian government said that 4.5 million people need food aid there, 40 percent more than last year. Jason Frasier, mission director of USAID in Ethiopia, the U.S. government aid arm, suggested that Ethiopia might even be undercounting those who need help. 
 
 Aid agencies have appealed for more than $100 million in emergency funding while warning of dire consequences if help does not arrive. 

 Image caption Somalis are fleeing to Ethiopia, Kenya and the capital, Mogadishu, in search of food 
 
 The UN has made its first aid delivery to drought victims in areas of Somalia controlled by al-Qaeda-linked militants since they lifted an aid ban. 
 
 UN children organisation's Rozanne Chorlton said al-Shabab had given UN workers unhindered access and hoped this would encourage other agencies. 
 
 It comes as the UK pledged £52.25m ($84m) in emergency drought aid. 
 
 But the UK's overseas aid minister told the BBC the UK would not deal with al-Shabab, which controls much of Somalia. 
 
 Andrew Mitchell is touring the huge Dadaab camp in north-eastern Kenya to see the scale of the crisis caused by the drought, the Horn of Africa's worst in 60 years which is estimated to be affecting some 10 million people. 
 
 'Close to famine' 
 
 Unicef airlifted food and medicine to malnourished children to the central town of Baidoa, more than 200km (about 125 miles) north-west of the capital, Mogadishu. 
 
 Ms Chorlton, the Unicef representative for Somalia, said al-Shabab had assured the agency it could operate without undue interference. 
 
 Media caption Andrew Mitchell: "Britain is putting its shoulder to the wheel... to stop this becoming a catastrophe" 
 
 Al-Shabab, which rules over large swathes of south and central Somalia, had imposed a ban on foreign aid agencies in its territories two years ago, accusing them of being anti-Muslim. It lifted the ban 10 days ago as long as groups had "no hidden agenda". 
 
 "They gave assurances that our access for humanitarian purposes would be unhindered and that we would be able to reach the people who need support most," Ms Chorlton told the BBC. 
 
 Unicef paid no fees to al-Shabab, and that the success of the mission meant it would be repeated in the near future, she added. 
 
 She warned the situation was close to famine. 
 
 Thousands of people have been fleeing al-Shabab's territories in search of food and water - some to Mogadishu, where aid agencies are operating in areas controlled by the the weak interim government, and others to Ethiopia and Kenya. 
 
 Some 1,400 Somali refugees are arriving every day at Kenya's overcrowded Dadaab camp - some walking up to 20 days to get there. 
 
 'Catastrophe' 
 
 Mr Mitchell, the UK's international development secretary, estimates that there are about 400,000 people in the camp. Aid agencies fear numbers could rise to half a million. 
 
 "More than 3,000 people every day are fleeing over the borders to Ethiopia and Kenya, many of them arriving with starving children," Mr Mitchell said. 
 
 "We need everyone who can help from across the world now to make sure they focus on this developing crisis here to stop it becoming a catastrophe. There is an emergency developing of profound proportions," said the minister. 
 
 "Britain, as always, has shown huge generosity and is in a leadership position to try and resolve this crisis. We need others to do so too. We need the whole of the international community now to bend every sinew to help these poor people here who are in a desperate condition." 
 
 He said the UK's aid package would also help victims of the drought who remain in Somalia, which has been racked by constant war for more than 20 years - its last functioning national government was toppled in 1991. 
 
 "We simply will not deal with al-Shabab and we will not allow our operations to be fettered by them," said Mr Mitchell. 
 
 "We must be able to see that it can actually reach, with lifesaving provision, those for whom it is intended, then we will be giving additional support inside Somalia now and scaling that up." 
 
 The UK's £52.25m aid package comes after a joint charity appeal by the Disasters Emergency Committee (DEC) saw more than £13m raised in a week. 
 
 The cash is in addition to the £38m food aid package announced on 3 July to feed 1.3m people for three months. 
 
 The Department for International Development (Dfid) said the money would help:
– UN aid groups have finally begun delivering supplies to areas controlled by islamist militants in Somalia, as the Horn of Africa faces its worst drought in 60 years, reports the BBC. Al-Shabab, an al-Qaeda-linked militant group, banned international aid groups two years ago, but tens of thousands of refugees streaming out of their territory in search of help finally forced al-Shabab to lift that ban 10 days ago. "They gave assurances that our access for humanitarian purposes would be unhindered and that we would be able to reach the people who need support most," said UNICEF's rep for Somalia. The first aid, a five-ton air drop of food, clean water equipment, and medicine, was flown in Wednesday, to an area 125 miles northwest of Mogadishu. But with vast demand from more than 10 million people needing help in Somalia, Kenya, and Ethiopia, aid agencies are hoping to drum up $100 million in additional aid. "More children have died of malnutrition in the first four months of this year than in the whole of last year," one aid worker tells MSNBC.