Israeli battle tanks have been deployed along Gaza
Israeli battle tanks have been deployed along the border with Gaza. AFP

Israeli forces were Sunday readying for a looming Gaza ground invasion aimed at destroying Hamas, the Palestinian Islamist militant group that unleashed the bloodiest attack in the country's history.

In the eight days since Hamas gunmen killed more than 1,300 Israelis in their surprise onslaught, Israel has responded with a devastating bombing campaign that has claimed over 2,300 lives in Gaza.

Entire Gaza city blocks lie in ruins and hospitals are overflowing with thousands of wounded in the besieged territory, but there were fears of worse to come.

A bereaved and infuriated Israel has massed forces outside the long-blockaded enclave of 2.4 million people ahead of what the army has said will be a land, air and sea attack involving a "significant ground operation".

Prime Minister Benjamin Netanyahu, wearing a flak jacket, visited front line troops Saturday. "Are you ready for what is coming?" he said. "More is coming."

Special forces have made forays into Gaza and recovered the bodies of some of the up to 150 hostages feared taken by Hamas, the army said. Israel has said it has identified 120 captives, while Hamas has claimed 22 have died in Israeli air strikes.

A ground invasion threatens to bring the kind of gruelling house-to-house fighting that devastated Iraq's Mosul and Fallujah in years past, further complicated by Hamas' vast tunnel network.

Israel has warned 1.1 million Palestinian civilians to leave northern Gaza and a steady stream of families in overloaded cars, trucks and donkey carts have since headed south.

Israel has accused Hamas of blocking them from fleeing in order to use them as "human shields".

Alarm has grown about a wider humanitarian crisis in Gaza where Israel has cut off water, food and power, vowing to maintain the complete siege until all hostages are freed.

Fear and chaos reigned in the 40-kilometre (25-mile) long strip that is one of the world's most densely populated areas, with no place for large numbers of internally displaced people to flee to.

"The situation is catastrophic," said Jumaa Nasser, who travelled from Beit Lahia in northern Gaza with his wife, mother and seven children.

"We've had no food or sleep. We don't know what to do. I've given my fate up to God."

China's Foreign Minister Wang Yi charged that Israel's actions in Gaza have gone "beyond the scope of self-defence" and said it must "cease its collective punishment of the people of Gaza".

Egypt to the south controls the only other crossing with Gaza but has so far refused to open it for Palestinian or foreign refugees unless aid convoys are allowed to enter, according to unnamed intelligence sources cited in media reports.

Anger has flared in much of the Muslim world and beyond, with pro-Palestinian protesters burning Israeli and American flags.

Militant groups allied with Israel's arch foe Iran have a strong presence in neighbouring Lebanon and Syria, heightening the risk of a multi-front war for Israel.

The past week has seen repeated clashes on Israel's northern border with Lebanon where the Iran-back Hezbollah movement has tried to send small groups of militants across the border.

The United States has deployed a second aircraft carrier to the region in an effort to "deter hostile actions against Israel", Secretary of Defense Lloyd Austin said.

The mood in Israel has swung between collective grief, fury and a strong desire to punish Hamas which Netanyahu has likened to the Islamic State group.

Public outrage has been fuelled by images virally shared on social media of Israeli youths and families shot, stabbed and burnt in the Hamas attack.

The army said Sunday a strike had killed Billal Al Kedra, the Hamas commander "responsible for the Kibbutz Nirim massacre" where residents were killed in the homes and others were under siege for nine hours before soldiers came to their rescue.

The army has called up 300,000 reserve units and sought to quickly refresh their skills in training courses, while convoys of trucks have rushed tanks to the south.

Plane loads of Israelis have returned from around the world to join the latest of the many wars in Israel's 75-year history.

More ominously, an underground parking lot in the coastal city of Haifa has been converted into a trauma hospital.

Over the past week, Israel has levelled more than 5,500 buildings in Gaza while Hamas has fired thousands of rockets at Israel, most intercepted by missile defence systems.

Gaza's electricity outage threatens to cripple the enclave's life-support systems, from sea water desalination plants to food refrigeration and baby incubators in hospitals.

US President Joe Biden told Netanyahu in a call Saturday that the United States was working with the United Nations, Egypt, Jordan and others "to ensure innocent civilians have access to water, food, and medical care".

The White House said Biden also spoke with Palestinian leader Mahmud Abbas and pledged "full support" to the Palestinian Authority in its efforts to bring humanitarian assistance to Palestinians, "particularly in Gaza".