JERUSALEM — The Israeli military pulverized the Hamas -ruled Gaza Strip with airstrikes and kept blocking deliveries of food, water, fuel and electricity Thursday ahead of a possible ground invasion as Palestinians tried to stock up on supplies.

Israel said that nothing would be allowed into Gaza until the release of around 150 hostages taken captive by Hamas during an unprecedented surprise attack Saturday into Israel that also left hundreds killed.

U.S. Secretary of State Antony Blinken vowed American support for Israel Thursday in a meeting with Israeli Prime Minister Benjamin Netanyahu.

International aid groups warned of a worsening humanitarian crisis after Israel prevented entry of supplies from Egypt to Gaza’s 2.3 million people. The Israel-Hamas war has claimed at least 2,700 lives on both sides.

As the Israeli military retaliates for the Hamas attack, Palestinians say civilians are paying the price in strikes on Gaza, a small coastal strip of land.

Near-constant airstrikes that level entire neighborhoods have forced some 340,000 people to flee their homes, according to the U.N. Most have crowded into U.N. schools. Others sought the shrinking number of safe neighborhoods. Gaza is only 25 miles long, wedged among Israel, Egypt and the Mediterranean Sea.

While Israel has insisted that it is giving advance notice of its strikes, it is employing a new tactic of leveling whole swaths of neighborhoods, rather than just individual buildings.

Palestinians were in near-total darkness overnight after the only power station ran out of fuel and shut down. Hospitals' supplies of medicine and fuel for emergency generators are also expected to run out within days.

The morgue at Gaza’s biggest hospital overflowed Thursday as bodies came in faster than relatives could claim them on the sixth day of Israel’s heavy aerial bombardment.

With scores of Palestinians killed each day, medics in the besieged enclave said they have run out of places to put remains pulled from the latest strikes or recovered from the ruins of demolished buildings.

The morgue at Gaza City’s Shifa hospital can only handle some 30 bodies at a time, and workers had to stack corpses three high outside the walk-in cooler and put dozens more, side by side, in the parking lot. Some were placed in a tent, and others were sprawled on the cement, under the sun.

Internet connectivity in Gaza City has been below 20% since Tuesday, according to analyst Doug Madory of the network monitoring firm Kentik Inc., whose data shows outages began Saturday morning.

Madory said an internet provider in Gaza told him that Israeli air strikes had cut fiber optic cables.

The Israeli military says it is preparing for a possible ground operation in Gaza but that political leadership has not yet decided on one. Lt. Col. Richard Hecht told reporters Thursday that forces “are preparing for a ground maneuver if decided.”

Israel’s government is under intense pressure from the public to topple Hamas, which has ruled Gaza since 2007. Israel has called up some 360,000 army reservists and has threatened an unprecedented response to Hamas’ wide-ranging incursion over the weekend.

The Israeli military said more than 1,300 people, including 222 soldiers, have been killed in Israel — a staggering toll unseen since the 1973 war with Egypt and Syria that lasted weeks.

The Israeli military said it is currently targeting Hamas’ senior military and political leaders, whom it blames for the weekend attack.

Four previous rounds of Israel-Hamas fighting between 2008 and 2021 all ended inconclusively, with Hamas battered but still in control. Removing it from power would likely require reoccupying Gaza, at least temporarily. Even then, Hamas has a long history of operating as an underground insurgency in areas controlled by Israel.

The risk of the war spreading beyond Gaza was evident Wednesday, when the Iranian-backed 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 Thursday, Syrian state media reported that Israeli airstrikes hit the international airports of the Syrian capital Damascus and the northern city of Aleppo, damaging their runways and putting them out of service.

Israel appears increasingly likely to launch a ground offensive into Gaza, something it has done in two of its previous four wars with Hamas. The Israeli military has invested tremendous resources for such a scenario, even building a training base in its southern desert meant to replicate Gaza’s urban landscape.

A ground offensive would send a strong message, and forces operating inside Gaza might have a better chance of killing top Hamas leaders and rescuing hostages.

Such an assault all but guarantees far higher casualties on both sides. And it would involve street-by-street battles with Hamas militants who’ve had years to prepare tunnels and traps.

Blinken told Netanyahu Thursday that “you may be strong enough on your own to defend yourselves, but as long as America exists you will never have to ... We will always be there by your side.”

British Foreign Secretary James Cleverly arrived in Israel on Wednesday to express “unwavering solidarity” with the country following the attacks by Hamas, while Britain’s King Charles III condemned the “barbaric acts of terrorism in Israel,” a palace official said Wednesday. The German government held a minute of silence Wednesday in parliament for the Israeli victims of the Hamas attacks.

Malaysian Foreign Minister Zambry Abdul Kadir slammed Israel’s “outrageous acts of cruelty” in cutting off food, water and fuel to the Gaza Strip and said Malaysia will provide an emergency fund to help Palestinians.

Turkey is holding negotiations for the release of civilian hostages held by Hamas, a Turkish official said Wednesday.

Egypt has engaged with intensive talks with Israel and the United States to allow the delivery of aid and fuel through its Rafah crossing point. However, it pushed back against proposals to establish escape corridors out of Gaza, saying an an exodus of Palestinians from the enclave would have grave consequences on the Palestinian cause.

Dozens of citizens of other countries were killed or abducted in Saturday's attack, who were in Israel for reasons ranging from raves to agricultural work.

The number of U.S. citizens confirmed to have been killed in the latest Israel-Hamas war has risen to at least 25, Blinken said Thursday during his visit in Tel Aviv with Netanyahu. The State Department has said at least 17 more Americans remain unaccounted for and China, Brazil, Estonia and Turkey have all reported citizens dead or missing.

Hamas, which seeks Israel’s destruction, says it is defending Palestinians’ right to freedom and self-determination.

But the devastation following Hamas' surprise attack on Saturday has sharpened questions about its strategy and objectives. Hamas officials have said they planned for all possibilities, including a punishing Israeli escalation.

Desperation has grown among Palestinians, many of whom see nothing to lose under unending Israeli control and increasing settlements in the West Bank, the blockade in Gaza and what they see as the world’s apathy.

In addition to citing long-simmering tensions, Hamas officials cite a long-running dispute over the sensitive Al-Aqsa Mosque that is sacred to both Muslims and Jews. Competing claims over the site, known to Jews as the Temple Mount, have spilled into violence before, including a bloody 11-day war between Israel and Hamas in 2021.

Hezbollah, which like Hamas is supported by Iran, has so far been on the fence about joining the fighting. While Israel’s political and military leaders weigh the next move, they are nervously watching Hezbollah on Israel’s northern border and have sent troop reinforcements to the area. Hezbollah, with an arsenal of tens of thousands of rockets and missiles capable of hitting virtually anywhere in Israel, is viewed as a far more formidable foe than Hamas.

The U.S. and Qatar have agreed not to act on any Iranian request to access $6 billion in funds that were transferred from South Korea after a blanket waiver by Biden’s administration meant to clear the way for the release of five Americans held by Iran, a U.S. official said Thursday.

The move stops short of freezing the funds. Under the terms of the agreement, the funds must be requested by Iran and can go only for humanitarian purposes. The Americans were released last month.

The official was not authorized to speak publicly about the agreement and spoke to The Associated Press on condition of anonymity.

The funding has been a concern as questions mount about Iran’s influence or role in the Hamas attack on Israel. Iran is Hamas’ principal financial and military sponsor, though the White House says it has not uncovered information that Iran was directly involved in the operation.