Israeli air strikes on Wednesday smashed entire Gaza Strip neighbourhoods to rubble and left unknown numbers of bodies beneath mounds of debris. The bombardment raged on even though Hamas militants are holding an estimated 150 people snatched from Israel — soldiers, men, women, children and older adults.

“We will not allow a reality in which Israeli children are murdered,” Israeli Defence Minister Yoav Gallant said in a meeting with soldiers near the southern border on on Tuesday. “I have removed every restriction — we will eliminate anyone who fights us, and use every measure at our disposal.”

The Hamas-run Interior Ministry said Israeli air strikes destroyed the entire al-Karama neighborhood in Gaza City, with a “large number” of people killed or wounded. It said medical teams were unable to reach the area because all roads to it were destroyed.

Exchanges of fire over Israel’s northern borders with militants in Lebanon and Syria, meanwhile, pointed to the risk of an expanded regional conflict.

On Wednesday, the Lebanese militant group Hezbollah fired anti-tank missiles at an Israeli military position and claimed to have killed and wounded troops.The Israeli military confirmed the attack but did not comment on possible casualties. The Israeli army shelled the area in southern Lebanon where the attack was launched.

On Wednesday, an AP reporter witnessed waves of rockets rain down on Ashkelon, with shrapnel slamming into the street and Israel’s Iron Dome missile defence system intercepting at least one overhead. Residents screamed and wept as they heard the explosions.

In a new tactic, Israel is warning civilians to evacuate whole neighbourhoods — rather than just individual buildings — then inflicting devastation, in what could be a prelude to a ground offensive.

“The objective is for this war to end very differently from all of the previous rounds. There has to be a clear victory,” said Chuck Freilich, a former deputy national security adviser in Israel. “Whatever has to be done to fundamentally change the situation will have to be done.”

Palestinians struggled to find any safe area as Israeli strikes demolished the tiny coastal enclave, hospitals ran low on supplies and the territory’s only power plant ran out of fuel, deepening the misery of a war sparked by a stunning and deadly assault by Hamas militants.

Israel has vowed unprecedented retaliation against the Hamas militant group ruling the Palestinian territory after its fighters stormed through the border fence on Saturday and gunned down hundreds of Israelis in their homes, on the streets and at an outdoor music festival.

Since then, Hamas militants have continued to fire rockets at Israel, including a heavy barrage at the southern town of Ashkelon on Wednesday.

The war, which has already claimed at least 2,200 lives on both sides, is expected to escalate and compound the misery of people living in Gaza, where basic necessities and electricity were already in short supply.

After the attack, Israel stopped the entry of food, water, fuel and medicine into the territory — a 40-kilometre strip of land wedged among Israel, Egypt and the Mediterranean Sea that is home to 2.3 million Palestinians.

The sole remaining access from Egypt was shut down on Tuesday after airstrikes hit near the border crossing.

As Palestinians crowded into UN schools and a shrinking number of safe neighbourhoods, humanitarian groups pleaded for the creation of corridors to get aid in, warning that hospitals overwhelmed with wounded people were running out of supplies.

“There is no safe place in Gaza right now,” journalist Hasan Jabar said after three Palestinian journalists were killed in the bombardment of a downtown neighbourhood home to government ministries, media offices and hotels. “I am genuinely afraid for my life.”

Gaza’s only power plant ran out of fuel on Wednesday afternoon, forcing it to shut down after Israel cut off supplies, the Energy Ministry said. That leaves only generators to power the territory, but they also run on fuel that is in short supply.

The UN’s World Health Organisation said that supplies it had pre-positioned for seven hospitals have already run out amid the flood of wounded. Doctors Without Borders said surgical equipment, antibiotics, fuel and other supplies were running out at two hospitals it runs in Gaza.

Israel has mobilised 360,000 reservists and appears increasingly likely to launch a ground offensive into Gaza, with its government under intense public pressure to topple Hamas, which has ruled the territory since 2007 and remained firmly in control through four previous wars.

That would likely require a prolonged ground assault and reoccupying Gaza, at least temporarily. Even then, Hamas has a long history of operating as an underground insurgency in areas controlled by Israel.