Rafah (Gaza Strip) | The U.N. agency for Palestinian refugees warned Wednesday that without immediate deliveries of fuel it will soon have to sharply cut back relief operations across the Gaza Strip, which has been blockaded and hit by devastating Israeli airstrikes since Hamas militants launched an attack on Israel more than two weeks ago.

The warning came as hospitals in Gaza struggled to treat masses of wounded with dwindling resources, and health officials in the Hamas-ruled territory said the death toll was soaring as Israeli jets continued striking the territory overnight into Wednesday.

The Israeli military said its strikes had killed militants and destroyed tunnels, command centres, weapons storehouses and other military targets, which it has accused Hamas of hiding among Gaza's civilian population. Gaza-based militants have been launching unrelenting rocket barrages into Israel since the conflict started.

The Hamas-run Gaza Health Ministry said the airstrikes killed at least 704 people between Monday and Tuesday, mostly women and children. The Associated Press could not independently verify the death tolls cited by Hamas, which says it tallies figures from hospital directors.

The death toll was unprecedented in the decades-long Israeli-Palestinian conflict. Even greater loss of life could come when Israel launches an expected ground offensive aimed at crushing Hamas militants.

Israel said Tuesday it had launched 400 airstrikes over the past day, an increase from the 320 strikes the day before.

The U.N. says about 1.4 million of Gaza's 2.3 million residents are now internally displaced, with almost 600,000 crowded into U.N. shelters.

Gaza's residents have been running out of food, water and medicine since Israel sealed off the territory following the attack on southern Israel by Hamas, which is sworn to Israel's destruction.

In recent days, Israel allowed a small number of trucks filled with aid to come over the border with Egypt but barred deliveries of fuel — needed to power hospital generators — to keep it out of Hamas' hands.

The U.N. said it had managed to deliver some of the aid in recent days to hospitals treating the wounded. But the U.N. agency for Palestinian refugees, the largest provider of humanitarian services in Gaza, said it would run out of fuel by Wednesday night.

Officials said they were forced to reduce their operations as they rationed what little fuel they had.

“Without fuel our trucks cannot go around to further places in the Strip for distribution,” said Lily Esposito, a spokesperson for the agency. “We will have to make decisions on what activities we keep or not with little fuel.” Meanwhile, more than half of Gaza's primary health care facilities, and roughly a third of its hospitals, have stopped functioning, the World Health Organization (WHO) said.

Overwhelmed hospital staff struggled to triage cases as constant waves of wounded were brought in. The Health Ministry said many wounded are laid on the ground without even simple medical aid and others wait for days for surgeries because there are so many critical cases.

The Health Ministry says more than 5,700 Palestinians have been killed in the war, including some 2,300 minors. The figure includes the disputed toll from an explosion at a hospital last week.

The fighting has killed more than 1,400 people in Israel — mostly civilians slain during the initial Hamas attack, according to the Israeli government. Hamas is also holding some 222 people that it captured and brought back to Gaza.

Across central and south Gaza, where Israel told civilians to take shelter, there were multiple scenes of rescuers pulling the dead and wounded out of large piles of rubble from collapsed buildings. Graphic photos and video shot by the AP showed rescuers unearthing bodies of children from multiple ruins.

A father knelt on the floor of the Al-Aqsa Hospital in Deir Al-Balah next to the bodies of three dead children cocooned in bloodied sheets. Later at the nearby morgue, workers prayed over 24 dead wrapped in body bags, several of them the size of small children.

Buildings that collapsed on residents killed dozens at a time in several cases, witnesses said. Two families lost 47 members in a leveled home in Rafah, the Health Ministry said.

In Gaza City, at least 19 people were killed when an airstrike hit the house of the Bahloul family, according to survivors, who said dozens more remained buried. The legs of a dead woman and another person, both still half buried, dangled out of the wreckage where workers dug through the dirt, concrete and rebar.