It was an image that conveyed the human cost of the Pakistani floods – and the failure to deliver aid to those affected – more powerfully than any statistic: four young children lying on a filthy patchwork quilt, one of them sucking on an empty yellow bottle, all of them covered by flies.

The photograph by Associated Press's Mohammad Sajjad went around the world and featured in the Guardian's Eyewitness slot last week. The Guardian identified the child with the bottle as two-year-old Reza Khan and tracked him down to a makeshift camp at a roadside in Azakhel, some 19 miles from Peshawar, the capital of the insurgency-plagued province of Khyber Pakhtunkhwa, bordering Afghanistan.

The camp is a hotchpotch of about two dozen tents donated by various aid organisations, but it is run by none. Its residents must fend for themselves, and rely on the charity of passersby. There are 19 families here, all of them Afghan refugees: people who were displaced once by conflict in their homeland have now been displaced again by the month-long deluge.

Reza's family is from Butkhak, near the Afghan capital, Kabul. His father fled the area as a young boy, some 30 years ago, to escape the cycle of foreign occupation and internecine battles plaguing his homeland.

When we found him, Reza was in a tent with his mother, Fatima, who, like most Afghans, has only one name, and six of his seven siblings, all huddled on a blue blanket extended over the muddy floor. He was still clutching the same bottle. It was still empty.

Fatima tried to calm the boy, who cries in a constant, low whimper, as well as his twin brother, Mahmoud. She covered three of her other children – she has eight, all under the age of nine – with a dirty mosquito net somebody in a passing car gave her, but it has several gaping holes. Her eldest child, a nine-year-old girl called Sayma, is mute and seems dissociated from her surroundings. Her green eyes stare blankly ahead, seemingly oblivious to her brothers' wails. Flies carpet the few blankets arranged on the floor, and swarm all over the children. There is precious little in the tent – one cooking pot, a few cushions and two or three items of children's clothing. The stench of human and animal waste is overwhelming in the hot, humid air. There is no sanitation, just shallow, open ditches of raw sewage that attract flies and mosquitoes.

"They have had nothing to eat today. I have no food," Fatima says as she tries to swat the flies away from her children with a bamboo fan. "He's crying with hunger," she says, pointing to Reza. "It's been a month since he had any milk."

Two-year-old twins Reza and Mahmoud Khan sit with their mother Fatima and six other siblings in a roadside tent. Photograph: Jason Tanner for the Guardian

On this day, Reza's father, Aslam, was in a nearby hospital with his seven-year-old daughter, who has a skin infection caused by the unsanitary living conditions. Reza and several of his siblings also bear red spots, and appear malnourished. Their thin hair is coming out in clumps, their mother says. "We have been here for a month, a month!" Fatima says. "We are tired of these flies and of being without food. Before the waters came, my husband worked. We were poor before, but we had full stomachs."

The family of 10 used to live among the 23,000 residents of the Azakhel Afghan refugee camp, about 20 minutes' walk from their current roadside location. Aslam sold chickens for a living, travelling from door to door on a rickety bicycle, one of the family's prized possessions. He made about $2 a day.

Their mud-brick home was small, Fatima says, but it was enough for her. They lived among her husband's clan, about six families in all. "I had a kitchen, and there was a water tap close by," she says as her youngest child, one-year-old Ayad, tugs on her lilac dupatta, the scarf Pakistani women drape over their heads, arms and chest, pulling it away from her hair. She quickly readjusts the worn, holed fabric. "These clothes are all that we have now," she says, almost apologetically.

The loose mud bricks of their home were no match for the raging waters of the nearby swollen Kabul River. The floodwaters gushed into the house in the morning. She and her husband snatched several of the children in their arms, while extended family members helped bundle the others out of the house.

The clan of some 60 people walked toward the main road linking the town of Nowshera to Peshawar. They spent five days out in an open field, eating whatever scraps they could forage.

Aslam's older brother, Taykadar, set out on foot to find help, stopping at several of the dozen or so organized relief camps nearby. "They would ask us for our Pakistani identification cards in order to register us, but we are Afghans," he says. "And we are too many, that's the problem. We don't want to be split from each other. We've already lost our homes, we don't want to lose our families."

The men managed to obtain several tents from various organisations. Fatima's, for example, was donated by the Saudi government while others bear the logos of UNHCR. The Afghans say they have nothing to return to. Taykadar says they haven't received any help from a government he knows is overwhelmed by the destitution of its own people. The busy road that they have camped alongside is now their lifeline. Men, women and children rush out towards any car that appears to slow down alongside them. Hundreds of hands stretch out, hoping for food, water or clothing.

"We have to run after the food, it isn't given by some organisation in the tents," Fatima says bitterly. Her children eat once a day, usually in the evenings, thanks to charity organisations that provide iftar meals during Ramadan. But Ramadan ends this week. "I just want to say to the world, isn't there any way they can get us food?" she pleads. "Look," she says, pointing to the twins in her lap. "Please, our children are dying of hunger."