(AFP) - Israelis on Tuesday mourned and demanded answers over the army's biggest single-day losses since ground operations in Gaza started amid growing pressure on the government to end the conflict.

Twenty-one of the 24 troops killed on Monday were reservists slain "when a squad of terrorists surprised the force" with fire from a rocket-propelled grenade, military spokesman Daniel Hagari said.

The army said the grenade hit a tank and two buildings they were trying to blow up.

Prime Minister Benjamin Netanyahu said an investigation was launched into the "disaster" and that Israel "must learn the necessary lessons".

More than 200 people attended the funeral of one of the reservists, Hadar Kapeluk, whose coffin was draped with an Israeli flag, at Mount Herzl military cemetery in Jerusalem.

"The price of the war is heavy and painful," Hagari told a news conference later.

Israela Oron, of the Ben-Gurion University of the Negev, said the mounting toll of soldiers killed -- now 221 -- since Israel launched its ground offensive in Gaza will heap pressure on the government.

"Everybody is mourning the soldiers... people will demand clear answers about the purpose and the goal of this operation in Gaza."

- Khan Yunis 'encircled' -

On the ground, fighting raged in Khan Yunis, Gaza's main southern city, which the Israeli army said it had "encircled".

Gaza's Hamas-run health ministry said Israeli tanks fired on Nasser hospital in Khan Yunis on Tuesday, with "dozens expected wounded".

The Israeli military told AFP they were "not aware of the event" when asked about firing at the hospital.

The Palestinian Red Crescent said Israeli forces had hit its headquarters in Khan Yunis "resulting in injuries among internally displaced individuals who sought safety on our premises".

Hagari described the urban combat landscape as "very complex" but said troops "eliminated in the past day over 100 terrorists in the west of Khan Yunis".

UN agencies and aid groups have sounded the alarm about the growing threat of disease and famine in Gaza, where an estimated 1.7 million people are uprooted.

Gaza is "slipping every day into a much more catastrophic situation", said Abeer Etefa, senior Middle East spokeswoman for the World Food Programme.

The territory has "the largest concentration of people in what looks like famine-like conditions anywhere in the world", she added.

The Gaza war broke out with Hamas's unprecedented October 7 attacks, which resulted in the deaths of about 1,140 people in Israel, mostly civilians, according to an AFP tally based on Israeli official figures.

In response, Israel has carried out a relentless offensive that has killed at least 25,490 people in Gaza, around 70 percent of them women and children, according to the health ministry in the Hamas-run territory.

Militants also seized 250 hostages, and Israel says around 132 remain in Gaza. That number includes the bodies of at least 28 dead hostages, according to an AFP tally based on Israeli figures.

- Hopes for hostage deal -

Netanyahu's vow to destroy Hamas is increasingly seen within the cabinet as incompatible with returning hostages, experts say.

A week-long truce in November saw 105 hostages released, the Israelis among them in exchange for Palestinian prisoners held in Israeli jails.

US news outlet Axios reported on Monday that Israel had proposed to Hamas, via Qatari and Egyptian mediators, a new deal to free all the hostages over two months.

The report, citing unnamed Israeli officials, said the proposed deal would be carried out in multiple stages and involve releasing an undetermined number of Palestinian prisoners.

Qatar's foreign ministry declined to comment on the ongoing negotiations and said many media reports "are either missing elements or completely false".

The US coordinator for the Middle East, Brett McGurk, was in the region for meetings aimed at securing a new hostage exchange deal, the White House said.

A Palestinian source familiar with the talks told AFP a Hamas delegation arrived in Cairo on Tuesday to meet Egypt's intelligence chief and discuss new ceasefire proposals.

It comes as Netanyahu has come under increased fire over remarks rejecting Palestinian "sovereignty", with UN chief Antonio Guterres on Tuesday describing the rejection of a two-state solution as "unacceptable".

- US, UK hit Yemen's Huthis -

The Gaza war has spurred fears of a wider escalation, with a surge in violence involving Iran-backed Hamas allies across the region.

Lebanon's Shiite movement Hezbollah said Tuesday it struck the Israeli air control base of Meron for a second time in recent weeks, in response to Israeli "assassinations" and attacks on civilians.

Israel's military said air forces struck several locations in Lebanon on Tuesday, including a "military asset" used by Hezbollah and "operated by Iranian forces".

The army also said reservists killed a "terrorist" who opened fire on them in the occupied West Bank.

The United States and Britain launched new air strikes against Yemen's Iran-backed Huthi rebels on Tuesday over their attacks on Red Sea shipping.

The Huthis, who say their action targets Israeli-linked shipping in solidarity with Palestinians in Gaza, warned "these attacks will not go unanswered and unpunished".

© Agence France-Presse