Helmi Samouni knelt yesterday on the floor of the bedroom he once shared with his wife and their five-month old son, scraping his fingers through a thick layer of ash and broken glass looking for mementoes of their life together. "I found a ring. I might find more," he said.

His wife Maha and their child Muhammad were killed in the second week of Israel's 22-day war in Gaza when they were shelled by Israeli forces as they took shelter nearby along with dozens of relatives. In total 48 people from one family are now known to have died that Monday morning, 5 January, in Zeitoun, on the southern outskirts of Gaza City.

Of all the horrors visited on the civilians of Gaza in this war the fate of the Samounis, a family of farmers who lived close together in simple breeze-block homes, was perhaps the gravest.

Around a dozen homes in this small area were destroyed, no more than piles of rubble in the sand yesterday. Helmi Samouni's two-storey house was one of the few left standing, despite the gaping hole from a large tank shell that pierced his blackened bedroom wall. During the invasion it had been taken over by Israeli soldiers, who wrecked the furniture and set up sand-bagged shooting positions throughout.

They left behind their own unique detritus: bullet casings, roasted peanuts in tins with Hebrew script, a plastic bag containing a "High Quality Body Warmer", dozens of olive-green waste disposal bags, some empty, some stinking full - the troops' portable toilets.

But most disturbing of all was the graffiti they daubed on the walls of the ground floor. Some was in Hebrew, but much was naively written in English: "Arabs need 2 die", "Die you all", "Make war not peace", "1 is down, 999,999 to go", and scrawled on an image of a gravestone the words: "Arabs 1948-2009".

There were several sketches of the Star of David flag. "Gaza here we are," it said in English next to one.

Helmi's brother Salah, 30, had an apartment in the same house. He too was pulling out what he could, including an Israeli work permit once issued to his father. "They gave him a permit and then they came from Israel and they killed him," said Salah. In the attack he lost both his parents, Talal and Rahma, and his two-year-old daughter Aza.

During the war, Israel banned journalists from entering Gaza. But the accounts of Salah and his neighbours outside the rubble of their homes yesterday corroborate the accounts from witnesses given in the days after the attack, accounts which led the UN to describe the killings at Zeitoun as one of the gravest episodes of the war and the Red Cross to call it, in a rare public rebuke, "a shocking incident".

More than a dozen bodies were pulled from the rubble on Sunday, and one more yesterday, bringing the Samouni death toll to 48, according to Dr Mouawia Hassanein, head of Gaza's Emergency Medical Services. With more bodies being recovered each day, the death toll from Israel's three-week war now stands at 1,360. On the Israeli side, 13 were killed.

On the second Saturday of the war, after a week of Israeli air strikes, there came a wave of heavy artillery shelling which preceded the ground invasion of Gaza. That night, Salah Samouni took shelter on the ground floor with 16 others from his family. By the next morning, Sunday 4 January, more neighbours had come looking for shelter and the number now there was approaching 50.

"They fired a shell into the upstairs floor and it started a fire," said Salah. "We called the ambulance and the fire service, but no one was able to reach us." Soon a group of Israeli soldiers approached. "They came and banged on the door and told everyone to leave the house," he said. They walked a few metres down the dirt road and entered the large, single-storey home of Wa'el Samouni.

There they stayed for the rest of the day, now a group of around 100 men, women and children, with no food and little water. Though there may have been Palestinian fighters operating in the open fields around the houses, all the witnesses are adamant that those gathered in Wa'el Samouni's house were all civilians and all from the same extended family.

On the Monday morning, four of the men - Salah among them - decided to go out to bring back firewood for cooking. "They fired a shell straight at us," Salah said. Two of the four were killed instantly, the other two were injured. Salah was hit by shrapnel on his forehead, his back and his legs. Moments later, he said, two more shells struck the house, killing dozens of them.

Salah and a group of around 70 fled the house, shouting to the soldiers that there were women and children with them. They ran to the main road and on for a kilometre until ambulances could reach them. Others stayed behind.

Wa'el Samouni's father, Faris, 59, lived next door to the house where the crowd had taken shelter. He had a single-storey house with only a corrugated iron roof and so his family had moved next door to shelter, but he had stayed behind. He was unable to leave his building for fear of being shot, but on the Tuesday the survivors called to him to bring water. He ran quickly the short distance and joined them.

"Dead bodies were lying on the ground. Some people were injured, they were just trying to help each other," he said. There among the dead Faris found his wife Rizka, 50; his daughter-in-law Anan; and his granddaughter Huda, 16.

Only on the afternoon of the following day, the Wednesday, were the survivors rescued when the Red Cross arrived to carry them out to hospital.

The Israeli military has said it is investigating what happened at Zeitoun. It has repeatedly denied that its troops ordered the residents to gather in one house and said its troops do not intentionally target civilians.

Others in the family saw a different but equally grim fate. Faraj Samouni, 22, lived with his family next door to Helmi and Salah. Again on the Saturday evening the family had sought shelter from the heavy shelling, a group of 18 of them gathering in one room for the night. On the Sunday morning the Israeli soldiers approached. "They shouted for the owner of the house to come out. My father opened the door and went out and they shot him right there," said Faraj.

With the body of his father Atiya, 45, slumped on the ground outside, the soldiers fired more shots into the room, he said, this time killing Faraj's younger half-brother Ahmad, who was four years old, and the child's mother.

Yesterday there was blood on the wall of the small room where the child had been sitting.

Then the troops ordered them to lie on the floor. But when a fire started burning in the room next door, sending in acrid smoke, they began shouting to be allowed out. "We were shouting 'babies, children'," Faraj said.

Eventually the soldiers let them out and they ran along the street, passing the others who had gathered in Wa'el Samouni's house and making their way out on to the main road and to safety.

When Faraj returned, he found his home completely destroyed, a pile of twisted iron bars and concrete. On a small outdoor grill were the charred remains of the eight aubergines that the family had been cooking that Sunday morning for their breakfast.

Only on Sunday was he able to bury his father's body and even then there was a final injustice: Gaza's graves are now so crowded and concrete so scarce because of Israel's long blockade that he had to break open an older family grave and put his father in with the other corpse.

"How can we have peace when they are killing civilians, even children?" said Faraj. "I support the ceasefire now. We have no power. If there wasn't a ceasefire we couldn't even bury our dead."

Some Gazans speak privately of their anger at Hamas, blaming the Islamist movement that rules the small territory for dragging them into this conflict. But by far the larger majority are speaking now of their bitter anger at Israel and their deep resentment at the apathy of the Arab world and the rest of the international community, which failed to halt the destruction and the killing.

"We blame everyone," said Ibrahim Samouni, 45, who lost his wife and four of his sons in the killings at Zeitoun. "We need everyone to look at us and see what has happened here. We are not resistance fighters. We are ordinary people."