Gaza's only power plant has run out of fuel, forcing it to shut down after Israel cut off supplies, the Energy Ministry said Wednesday. That will leave only generators to power the territory.

The blackouts come as Israel has decided to block fuel shipments into the Gaza Strip as part of what the Israeli government has called a "complete siege" on the territory run by the Hamas militant group.

This comes after Palestinians in the sealed-off Gaza Strip struggled to find any safe area Wednesday, as Israeli strikes demolished entire neighbourhoods, hospitals ran low on supplies and a power blackout was expected within hours, deepening the misery of a war sparked by a stunning and deadly assault by Hamas militants.

Airstrikes smashed entire city blocks to rubble in the tiny coastal enclave and left unknown numbers of bodies beneath mounds of debris. The bombardment raged on even though militants are holding an estimated 150 people snatched from Israel — soldiers, men, women, children and older adults.

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

Since then, 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-kilometer-long (25-mile) 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 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 power authority says its sole power plant will run out of fuel within hours, leaving the territory without electricity after Israel cut off supplies. Palestinians there have long relied on generators to power homes, offices and hospitals, but have no way of importing fuel for those either.

The UN's World Health Organization 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.

In one, "we consumed three weeks worth of emergency stock in three days, partly due to 50 patients coming in at once," Matthias Kannes, the aid group's head of mission in Gaza, said Wednesday. He said the territory's biggest hospital, Al-Shifa, only has enough fuel for three days.

Israel has mobilized 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.

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

Israeli airstrikes late Tuesday struck the family house of Mohammed Deif, the shadowy leader of Hamas' military wing, killing his father, brother and at least two other relatives in the southern town of Khan Younis, senior Hamas official Bassem Naim told The Associated Press.

Deif has never been seen in public and his whereabouts are unknown.

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.

In a new tactic, Israel is warning civilians to evacuate whole neighborhoods —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."

Hamas officials have said they planned for all possibilities, including punishing Israeli escalation. Desperation has grown among Palestinians, many of whom see nothing to lose under unending Israeli military occupation and increasing settlements in the West Bank, a 16-year-long blockade in Gaza and what they see as the world's apathy.

The Hamas-run Interior Ministry said Israeli airstrikes destroyed the entire al-Karama neighbourhood 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. Rescue officials say they have struggled to enter other areas as well.

In another neighbourhood on Tuesday, Palestinian Civil Defense forces pulled Abdullah Musleh out of his basement together with 30 others after their apartment building was flattened.

"I sell toys, not missiles,'' the 46-year-old said, weeping. "I want to leave Gaza. Why do I have to stay here? I lost my home and my job."

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.

On Tuesday night, a group of militants entered an industrial zone in Ashkelon, sparking a gunbattle with Israeli troops, the military said.

Three militants were killed, and troops were searching the area for others. The Israeli military said more than 1,200 people, including 155 soldiers, have been killed in Israel, a staggering toll unseen since the 1973 war with Egypt and Syria that lasted weeks.

In Gaza, 1,055 people have been killed, according to authorities there; Israel says hundreds of Hamas fighters are among them. Thousands have been wounded on both sides.

The bodies of roughly 1,500 Hamas militants were found on Israeli territory, the military said. It wasn't clear whether those numbers overlapped with deaths reported by Palestinian authorities.

Days of clashes between rock-throwing Palestinians and Israeli forces in the West Bank have left 15 Palestinians dead. The violence also spread into east Jerusalem, where Israeli police said they killed two Palestinians who hurled stones at police late Tuesday.

In Gaza, more than 250,000 people have fled their homes, the UN said, the most since a 2014 air and ground offensive by Israel uprooted about 400,000.

The vast majority are sheltering in schools run by the UN agency for Palestinian refugees. Damage to three water and sanitation sites have cut off services to 400,000 people, the UN said.

Tens of thousands of people in southern Israel have been evacuated since Sunday.