One by one, relatives and neighbours used a sledgehammer to try to break apart the large chunks of concrete trapping the young boy.

His eyes closed and wearing a Spiderman sweater, the boy was visible but unreachable.

"The civil defence tried to retrieve people but couldn't get anyone out so they left," said Muhammad al-Deiri, a neighbour who had come to help.

Each strike of the sledgehammer echoed from the building's collapsed second floor through the eerily quiet surrounding streets of what was once a bustling city.

In the early hours of Tuesday, Israel launched its most intense air strikes since a ceasefire took hold in Gaza in January, killing more than 400 people according to the health ministry in the Hamas-run territory.

Israel vowed to keep up the pressure until the Palestinian Islamist movement Hamas releases the hostages still held in Gaza.

Of the 251 captives seized during Hamas's October 7, 2023 attack on Israel that triggered the war, 58 are still held in Gaza, including 34 the Israeli military says are dead.

Hamas says it is willing to negotiate and has called on the international community to act to bring the war to an end.

- 'Random bombings' -

In Gaza City's al-Sabra neighbourhood where the boy was trapped under rubble, surrounding buildings had also been damaged in the strikes.

Flattened floors lay atop one another.

"Random bombings started everywhere," said 21-year-old Sundus al-Imam.

"The Al-Hattab family's house -- our neighbours -- was hit, leaving some with minor injuries among us girls."

"Since (President Donald) Trump's time, the United States has been sending massive military aid to Israel, making it more powerful than before," she added.

Trump and Israeli Prime Minister Benjamin Netanyahu have promised "hell" for Hamas if the remaining hostages held in Gaza are not immediately released.

As part of its escalating pressure, Israel first blocked the entry of humanitarian aid into Gaza in early March, then cut the limited electricity supply to the territory's main water desalination plant.

Since then, humanitarian organisations operating on the ground have been reporting on the dire situation for the population.

Rafat Ramadan, another resident of al-Sabra, painfully remembered seeing "bodies hanging from the rubble, needing cranes to remove them".

Ramadan's own house was struck, trapping his daughters under concrete until he managed to free them with the help of his nephews.

They took the girls to Gaza City's Baptist Hospital, he said, only to find the facility overwhelmed.

"What we lived through was hell," said Ramadan, who says he lost his son in the war.

- 'Pray for your loved ones' -

After almost two months under the truce, Gazans are once again experiencing the panic of more than 15 months of war between Hamas and Israel.

In the courtyard of Al-Aqsa Hospital in central Gaza's Deir al-Balah, dozens of men gathered in mourning next to white plastic body bags.

They said that four members of the same family were caught by overnight bombing while reciting a traditional Ramadan prayer.

"Remember Allah, pray for your loved ones, your heart will be in peace," read a poster near the bodies.

A young man cried in silence while the body bags were loaded into a truck for burial.

The Israeli military urged residents of several areas in Gaza's border areas to evacuate "combat zones", in particular Beit Hanun, in the territory's far north.

Residents took to the road, mainly by foot -- and for most of them, not for the first time -- in order to seek shelter in Gaza City.

Children pulled water jerrycans next to donkey carts loaded with cheap foam mattresses, plastic bowls and tents.

Residents carried only the most basic necessities for daily life, nearly a year and a half after the war started.

Around them stood bombed-out buildings, piles of rubble and mountains of waste, while Israeli planes roared and drones buzzed above their heads.