Thousands of Somalis fleeing a bruising drought in the Horn of Africa are facing a long wait to enter overcrowded camps and receive aid when they cross into neighbouring Kenya.

Weakened by hunger at home, then by several days of walking or traveling on open trucks in the baking sun, the refugees are pouring into the area around Dadaab, the world's largest refugee camp.

"The cattle all died and we could not get any food so we fled," explained 32-year-old Maryan Abdullah, as her six small children huddled round her sharing the last of the milk that another family had given them.

"We travelled for seven days by road and when we arrived here last night I depended on handouts from neighbours to give the children something to eat," she said gesticulating at her offspring, most of whom were barefoot.

Maryan, her face framed in a voluminous blue headscarf, is just one among several hundred new arrivals waiting to get into Dadaab at the Dagahaley registration point.

"This drought was very severe, because it was the second in a row," explained Bashir, who like Maryan, comes from the Sokow district in south Somalia's Bay region.

"We were going without food, the animals were dying so we took the few remaining animals to the market and sold them and I received a big bag of Somali shillings," he explained.

With that he travelled for four days to the Somali border by lorry under the blistering sun then on the Kenyan side he took a bus to Dadaab.

This is his third day in the camp although he has not yet succeeded in registering and he has survived so far on food donated by other refugees.

He has joined more than 400,000 fellow Somalis who have fled two decades of war and serial droughts.

Several hours of waiting in the sun to register has started to fray tempers and has led inevitably to a "fast track" entry system for those with money to pay the guards.

Touts move up and down the queues and for a fee equivalent to just over 10 dollars arrange for families to jump the queue -- to the anger of the elders and of the new arrivals who do not have any money left.

Aid workers say the situation in Dadaab, which has been at bursting point for years, keeps on getting worse.

In June about 30,000 people -- most of them fleeing drought -- arrived at Dadaab, five times as many as a year earlier, according to UNHCR, the UN's refugee agency.

"We have registered a thousand people in one day," Idris Farah, the UNHCR's field co-ordinator at the camp told AFP. "Clearly the situation is getting worse."

Built to house 90,000 people and home to more than four times that number, Dadaab was already well over its maximum capacity before this latest influx.

"It still takes too much time for refugees to get proper assistance," Antoine Froidevaux, MSF's field coordinator in Dadaab told AFP. "The answer in terms of humanitarian aid is not satisfactory at all at the moment."