JERUSALEM >> The Israeli army said Tuesday that 21 soldiers were killed in the Gaza Strip in the deadliest attack on its forces of the 3-month-old war against the militant Hamas group.

The reservists were preparing explosives to demolish two buildings in central Gaza on Monday when a militant fired a rocket-propelled grenade at a tank nearby, Rear Adm. Daniel Hagari, the chief military spokesperson, said. The blast triggered the explosives, causing both two-story buildings to collapse on the soldiers inside.

The heavy death toll could add new momentum to calls for Israel to pause the offensive or even halt it altogether. Large numbers of Israeli casualties have put pressure on Israel’s government to halt past military operations.

Prime Minister Benjamin Netanyahu has vowed to press ahead until Israel crushes the ruling Hamas militant group and wins the freedom of over 100 hostages held captive in Gaza. Israelis are increasingly divided on the question of whether it’s possible to do either.

Families of the hostages and many of their supporters have called for Israel to reach a cease-fire deal, saying that 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 win their loved ones’ release.

Israel launched its offensive after Hamas’ Oct. 7 cross border attack that killed over 1,200 people and abducted some 250 others. More than 100 were released in November in exchange for a weeklong cease-fire and the release of 240 Palestinians imprisoned by Israel.

The offensive has caused widespread destruction, displaced an estimated 85% of Gaza’s population and left over 25,000 Palestinians dead, according to health officials in the Hamas-run territory. The United Nations and international aid agencies say the fighting has unleashed a humanitarian disaster, with a quarter of the area’s 2.3 million people facing starvation.

The war has heightened regional tensions, with Iran-backed groups in Lebanon, Syria, Iraq and Yemen attacking United States and Israeli targets in support of Palestinians. The U.S. and Britain launched another wave of strikes Monday against the Houthi rebels in Yemen, who have targeted international shipping in the Red Sea in what they portray as a blockade of Israel.

The attack that killed the soldiers occurred about 600 yards from the border in Maghazi, one of three built-up refugee camps in central Gaza dating back to the 1948 war surrounding Israel’s creation.

Ground operations have been focused on the camps, as well as the southern city of Khan Younis, after Israel claimed to have largely defeated Hamas in northern Gaza in operations that caused widespread destruction to that part of the territory, including Gaza City.

Dozens of Palestinians were killed Monday in heavy fighting in Khan Younis, where people dug graves in the courtyard of the city’s Nasser Hospital as staff struggled to deal with the large number of wounded people, including children.

Gaza’s internet and phone networks collapsed again Monday for the 10th time during the war, posing another challenge for first responders and making it impossible for people to reach loved ones in different parts of the territory.

Israel believes Hamas commanders may be hiding in vast tunnel complexes beneath Khan Younis, the hometown of the group’s top leader in Gaza, Yehya Sinwar, whose location is unknown. Hamas leaders are also believed to be using hostages as human shields, further complicating any rescue efforts.

The growing death toll and dire humanitarian situation have led to increasing international pressure to scale back the offensive and agree to negotiate the creation of a Palestinian state after the war. Netanyahu has rebuffed both demands.