Thousands of reservists have begun reporting for duty as the Israeli military presses ahead with its offensive to conquer Gaza City.

Ground forces are already pushing into the outskirts of Gaza's largest urban area, which the military has said is a stronghold of Hamas.

The city is also coming under heavy Israeli aerial and artillery bombardment, with local hospitals saying that more than 50 Palestinians have been killed there since midnight.

The military has ordered residents to evacuate and head south immediately. The UN says an estimated 20,000 have done so over the past two weeks, but almost a million remain.

UN humanitarian officials have warned that the impact of a full-blown offensive would be beyond catastrophic, not only for those in the city but for the entire Gaza Strip.

Last month, the Israel Defense Forces (IDF) announced a call-up of about 60,000 reservists ahead of Operation Gideon's Chariots II, the next phase of the ground offensive that has seen it take control of at least 75% of Gaza.

On Tuesday, an Israeli military official said thousands had begun reporting for duty.

Israeli media reported that many of the reservists would be deployed to the occupied West Bank and northern Israel to free up active-duty personnel for the offensive.

They also reported that some combat units were seeing lower turnout than for previous call-ups, with reservists who had already served several tours during the 22-month war requesting exemptions for personal or financial reasons.

Prime Minister Benjamin Netanyahu announced that Israel would conquer all of Gaza after indirect talks with Hamas on a ceasefire and hostage release deal broke down in July.

At a government meeting on Sunday, he said the security cabinet had agreed that the IDF's objectives were defeating Hamas and releasing all of our hostages.

The armed group is currently holding 48 hostages, 20 of whom are believed to be alive.

The families of hostages fear that the new offensive will endanger their loved ones and are demanding the prime minister negotiate an agreement for their release.

Stop the war and bring all the hostages home in a deal - the living and the dead alike - some for rehabilitation in their families' embrace, others for proper burial on Israeli soil, said the daughter of Ilan Weiss, one of the two hostages whose bodies were recovered by Israeli troops in Gaza last week.

The IDF's Chief of Staff, Lt Gen Eyal Zamir, has urged Netanyahu to accept a proposal from regional mediators that would lead to the release of about half of the hostages during a 60-day truce. However, Netanyahu has insisted on a comprehensive deal for the release of all hostages and the disarmament of Hamas.

There were reportedly tense exchanges between Zamir and ministers during a meeting on Sunday, where the general warned that the Gaza City offensive could endanger hostages and lead to the establishment of a military government there.

In an address to reservists at Nachshonim base in central Israel on Tuesday, Zamir declared that the IDF was preparing for nothing less than decisive victory.

We are going to increase and enhance the strikes of our operation, and that is why we called you, he said. We will not stop the war until we defeat this enemy.

On the ground in Gaza, hospital officials reported that Israeli strikes had resulted in at least 95 Palestinian deaths since midnight, with Al-Shifa hospital receiving 35 bodies from the latest strikes. The humanitarian situation is dire, with overcrowded hospitals and a looming food crisis.

The UN has indicated that forcing large populations to move could amount to a war crime and has described the ongoing famine conditions in Gaza as a man-made disaster. Israel disputes claims regarding the death toll from malnutrition but maintains that aid deliveries are uninterrupted.

The violence marks the continuation of a campaign initiated by the Israeli military following Hamas's attack on Israel on October 7, 2023, which claimed around 1,200 lives and led to the hostage situation that now looms heavily over ongoing military operations.