21 Israeli soldiers are killed in Gaza when RPG is fired at a nearby tank, detonating the demolition explosives they were preparing and causing two buildings to collapse on them

A deadly attack has killed 21 Israeli soldiers in Gaza, the country's military said, a major setback that could add to growing calls for a ceasefire.

Soldiers were preparing explosives to demolish two buildings in central Gaza on Monday when a terrorist fighter fired a rocket-propelled grenade at a nearby tank, according to Israeli media reports.

The blast caused the explosions, causing the buildings to collapse on the soldiers, killing 21 – the largest loss of life for the Israeli army since the start of the war.

Defense Minister Yoav Gallant said it was a “difficult and painful morning” but that Israel was determined to continue.

“This war will determine Israel's future for decades to come, and the fall of soldiers is a requirement to achieve the war's goals,” he wrote on X.

Israeli military spokesman Admiral Daniel Hagari told reporters that the IDF was “investigating the details of the event and the reasons for the explosion.”

The deadly attack came as Israeli forces continued to push deeper into the west of Khan Younis, the largest city in the southern Gaza Strip.

The operation reportedly included the storming of a hospital and the arrest of medical staff, Gaza Health Ministry spokesman Ashraf al Qidra told Reuters.

Earlier on Monday, the IDF said three soldiers were killed in a separate incident in southern Gaza, bringing the total IDF death toll for the day to 24.

Israeli Prime Minister Benjamin Netanyahu has vowed to continue until Israel crushes the ruling terror group Hamas and wins the freedom of more than a hundred hostages held captive in Gaza.

Israelis are increasingly divided over whether it is possible to do both.

Families of the hostages and many of their supporters have called on Israel to reach a ceasefire deal, saying time is running out to bring the hostages home alive.

On Monday, dozens of hostages' relatives stormed a parliamentary committee meeting demanding a deal to secure the release of their loved ones.

Monday's high death toll could give new impetus to calls for Israel to pause or even halt the offensive altogether.

Large numbers of Israeli casualties have put pressure on the Israeli government to halt previous military operations.

News of the attack came as a senior Egyptian official said Israel has proposed a two-month ceasefire during which the hostages would be released.

In return, Palestinians jailed by Israel and key Hamas leaders in Gaza would be released and allowed to move to other countries.

The official, who was not authorized to brief the media and spoke on condition of anonymity, said Hamas has rejected the proposal and insists no more hostages will be released until Israel ends its offensive and withdraws from Gaza.

The Israeli government declined to comment on the talks when contacted by the Associated Press, the news agency reported.

The official said Egypt and Qatar, which have brokered deals between Israel and Hamas in the past, are developing a multi-phase proposal to try to bridge the gaps.

Israel launched the offensive after Hamas' cross-border attack on October 7, which killed more than 1,200 people and kidnapped some 250 others.

The offensive has caused widespread destruction, displaced an estimated 85% of Gaza's population and killed more than 25,000 Palestinians, health officials in the Hamas-held territory said.

The UN and international aid agencies say the fighting has unleashed a humanitarian disaster, with a quarter of the region's 2.3 million people facing hunger.

The war has also increased regional tensions, with Iranian-backed groups in Lebanon, Syria, Iraq and Yemen attacking US and Israeli targets in support of the Palestinians.

The US and Britain launched a new wave of attacks on Monday against Yemen's Houthi rebels, who have targeted international shipping in the Red Sea in what they portray as an Israeli blockade.

The rising death toll and dire humanitarian situation have led to increasing international pressure on Israel to scale back the offensive and agree to a path toward the creation of a Palestinian state after the war. The United States, which has provided crucial military aid for the offensive, has joined these calls.

But Netanyahu, whose popularity has plummeted since October 7 and whose governing coalition is dependent on far-right parties, has rejected both demands.

Instead, he has said Israel will have to expand its operations and eventually take over the Gaza side of the border with Egypt, where hundreds of thousands of Palestinians fleeing other areas have been rounded up in crowded U.N.-run shelters and sprawling tent camps .

That sparked angry protests from the Egyptian government, which rejected Israeli accusations that Hamas was smuggling weapons across the heavily guarded border.

Diaa Rashwan, head of Egypt's state information service, said on Monday that any Israeli move to occupy the border area would “lead to a serious threat” to relations between the two countries, which signed a historic peace treaty more than four decades ago. Egypt is also very concerned about a possible influx of Palestinian refugees to the Sinai Peninsula.

Rashwan said Egypt had full control of the border after taking a number of measures in recent years, including the creation of a five-kilometer buffer zone and the construction of barriers above and below ground.

Egypt “is capable of defending its interests and sovereignty over its land and borders, and will not place it in the hands of a group of extremist Israeli leaders who are trying to drag the region into a state of conflict and instability,” Rashwan said.