In the Horn of Africa, unseen as yet by the world's television cameras, a pitiful trek of the hungry is taking place. Tens of thousands of children are walking for weeks across a desiccated landscape to reach refugee camps that are now overflowing. They are being driven there by one of the worst droughts in the region for 60 years which, combined with the war in Somalia and soaring food prices, is threatening a famine that could affect between eight and 10 million people.

The malnourished children, some of whom become separated from their parents on the way, are now arriving at the camps in northern Kenya at a rate of 1,200 every day. At the largest, built for 90,000, there are now nearly 370,000. Many have covered hundreds of miles on feet that are bare and bleeding. Some reach their goal barely able to stand. Most are exhausted, and dehydrated. All are hungry.

Aid agency after agency has told The Independent on Sunday in the past few days of the terrible plight of these families from Somalia and Ethiopia. Save the Children (SCF), like many charities so worried it has launched an emergency response to the crisis, said: "Some families have walked for over a month through sand and searing heat in search of food, water and shelter. Many discarded the few possessions they had along the way." The charity's Kenya programme director, Catherine Fitzgibbon, said: "Children have made long journeys in terrifying conditions, often losing their families along the way and arriving at the camps in desperate need of security, healthcare and a normal life."

Neil Thorns, Cafod's director of advocacy, who led an emergency conference on food shortages in Nairobi last week, said: "There's no rain, no crops and the livestock are dying. There is nothing on the horizon that will make any of that better, and it's almost certain it will get much, much worse. People are migrating in their tens of thousands, but there is nowhere better for them to go. Governments need to wake up to the urgency of the situation and take the action that is needed immediately."

Cafod said that one aid worker, Nelly Shonko, drove the 100-odd miles between Marsabit in northern Kenya and Moyale on the border with Ethiopia, "seeing hundreds of rural people moving the other way, carrying all their possessions in search of food for their livestock. She knew that the land they were walking towards was no better than where they'd come from."

Journeys of more than 300 miles are typical: SCF spoke to one woman, called Fatuma, who had walked from her home in Somalia for a month and a half with her four children aged between three and 10 to reach a Kenyan camp. She said: "The weather was very harsh. It was so hot, and there was very little shelter. I left my husband in Somalia. I do not know if I will see him again. The war in Somalia is very bad for families. The drought as well is just too much. We cannot cope. We had 15 goats. But they died one by one because of the drought. We had a well in my village, but it dried up. Then the one in the next village dried up."

Adan Kabelo, head of Oxfam's work in Somalia, said in a blog: "The situation here is truly shocking, and, as the local elders warned me, we are facing a terrible human catastrophe unless the world acts quickly."

This is a situation that has been brewing – and deteriorating – for a long time. Across much of Somalia and Ethiopia, the last two rains have failed – something which, says SCF's Andrew Wander, used to occur every 10 to 12 years, but now happens almost every other year. The UN's World Food Programme (WFP) says: "In June, the famine early-warning systems network said it had compared rainfall data for Kenya and Ethiopia and concluded that 2010-11 was the driest or second driest year since 1950-51 in 11 of 15 analysed pastoral zones. This does not, however, mean that this is yet the worst drought in the Horn of Africa. The 2007-09 drought, for instance, peaked in September 2009 with 22 million people in need of humanitarian assistance."

Nevertheless, many of the people in the region are pastoralists, and in some places about 70 per cent of livestock have died. Even in a place like Dobley in Somalia, where there has been a little recent rain, the situation is desperate. Oxfam reports that animal carcasses litter the road to the borehole and "there are hundreds of people and about 15,000 emaciated cows, camels, sheep, and goats crowded around trying to get water to stay alive". Oxfam is frantically trying to keep this borehole flowing. If its engineers fail, the outlook is not good. The next water point is 80km away.

Audrée Montpetit, senior humanitarian programme quality adviser at Care International, has recently visited the drought-affected region of Borena in Ethiopia. She said: "People are eating less, cutting trees to make charcoal and sell. Since there's no pasture, men are cutting trees to get leaves for their animals. Women, who are responsible for getting water, are having to travel six to 10 hours every day to get it. We've seen an increase in acute malnutrition but there's obviously a lot of water-borne disease too; that's been increasing. People accept that the worst is yet to come."

And the famine looms at a time when food prices have been increasing sharply for some time – and still are. Since last May, the price of maize has more than doubled in parts of Ethiopia, and that of red sorghum has risen in Somalia by 240 per cent. Even in Kenya, white maize now costs 58 per cent more than it did a year ago. And then there is the conflict in Somalia, which drives people to the camps and which, in much of southern and central parts of the country, severely limits humanitarian access.

Aid workers are beginning to wonder for how much longer the camps can contain the need. Dadaab, in Kenya, originally built to accommodate 90,000, now has 367,855 refugees, making it the world's largest refugee camp. There were plans for an extension, but the Kenyan government scotched that, and thousands now squat hopefully outside the perimeter.

And yet still people come. The numbers arriving at Dadaab's three camps are swelling at an alarming rate – 5,621 arrived in the last week of June compared with 1,866 in the first week of the month. According to the UN, more than half of the camps' refugees are children, and 153,525 of those are under the age of 11. There are also 12,328 people over the age of 60 in the camps, while 95 per cent of the total population are from Somalia, with the rest mainly from Ethiopia.

The overcrowding produces problems beyond comfort, food rations and sanitation. On Thursday, two people were killed and dozens injured when a riot broke out. The UN refugee agency said the "serious disturbance" occurred when authorities tried to demolish illegal buildings at a food distribution point.

Camps elsewhere are also reaching bursting point. Getinet Ameha, a WFP aid worker, visited two camps last week in Dolo Ado on the Somalia, Kenyan and Ethiopian border. Last week the government opened a third camp, Kobe, to deal with the 1,200 new arrivals each day. He said: "The majority of people in the camps are women and children, and it's very difficult because the camps were only built to hold 20,000 in each one and there's now almost 40,000 people living in each." Here, some 45 per cent of the new arrivals are malnourished – the threshold for declaring an emergency is 15 per cent. He added: "A lot of people are coming, 1,400 new people each day, but the WFP is providing food. There are problems with health. The people are having to live very close to each other. In one tent I witnessed a family of 12 together."

Aid agencies are doing all they can, but the "perfect storm" of drought, war and costly food is difficult to overcome when resources are so limited. SCF says it has less than half the money it needs for a proper response. And a statement from the WFP last week said bleakly: "The humanitarian response in Somalia and Ethiopia in particular is hampered by large funding shortfalls. New contributions are urgently needed or suffering will grow."

It continued: "In Somalia, having started cutting ration sizes from February, WFP in May had only enough food left to feed 63 per cent of the almost one million people that WFP had planned to be feeding in May ... Because of a lack of funding, WFP in Ethiopia reduced food rations in certain areas of the country from March onwards."

The international food security scale of one to five rates a few parts of Ethiopia, Somalia and Kenya as category two, "Stressed". Many areas are at three and four, "Crisis" and "Emergency", but none, as yet, is a five, "Catastrophe/Famine". Unless there is a rapid change in the weather, the war or the food supply, that day may not be long postponed.