GEOFF BENNETT: Welcome to the "NewsHour."

A third day of brutal fighting between Israelis and Palestinians centered on Gaza today, and it continues tonight.

AMNA NAWAZ: Israel has hammered the region with airstrikes and artillery, in retribution for Saturday's bloody terror attack by Hamas.

GEOFF BENNETT: Israeli Prime Minister Benjamin Netanyahu says the offensive has only begun, and that the ferocity of Israel's reprisals on Hamas will -- quote -- "reverberate with them for generations."

An Israeli ground invasion of Gaza is widely expected to begin in the coming hours and days.

AMNA NAWAZ: And, already, there are staggering death tolls, over 900 Israelis dead, thousands more wounded, while, in Gaza, nearly 700 Palestinians have been killed.

Among the dead so far, according to President Biden, are 11 Americans.

Special correspondent Leila Molana-Allen is on the ground in Israel and begins our coverage.

LEILA MOLANA-ALLEN: Towering plumes of smoke rose over the Gaza City skyline, as the Middle East woke up to another day of war.

Airstrikes pounded Jabalia, a refugee camp north of Gaza City.

Moments earlier, this was a bustling supermarket.

Bulldozers dug through the twisted wreckage of daily life, as crowds of people searched beneath the rubble for survivors.

As shelling devastated the Gaza Strip, Palestinians mourned 17 members of the Shana (ph) family killed when their home was destroyed.

AHMED SHAMALAKH, Palestinian Resident (through translator): Israeli forces hit the building without warning.

They did not ask us to evacuate.

They did not say anything.

Suddenly, we heard the airstrike and ran to the building.

We found out that it collapsed entirely.

LEILA MOLANA-ALLEN: Israel's military said it hit more than 1,000 targets in the besieged enclave.

The attacks have eviscerated downtown mosques like this one and left over 120,000 Gazans displaced.

Israel also says it leveled the northeastern neighborhood of Beit Hanoun, which had been used as a staging ground by Hamas, the militant group that staged its unprecedented incursion into Israel over the weekend.

Today, the prime minister of the Palestinian Authority in the West Bank, long at odds with Hamas, defended the surprise attack.

MOHAMMAD SHTAYYEH, Palestinian Prime Minister (through translator): These events and their consequences are the result of the Israeli government's policy of practicing the worst forms of aggression, killing, land confiscation, assault on holy sites, and the terrorism and heinous practices of the settlers.

LEILA MOLANA-ALLEN: Israeli Prime Minister Benjamin Netanyahu responded.

BENJAMIN NETANYAHU, Israeli Prime Minister (through translator): We have always known who Hamas is.

Now the entire world knows.

Hamas is ISIS, and we will defeat it just like the enlightened world defeated ISIS.

This vile enemy wanted war, and it will get war.

LEILA MOLANA-ALLEN: Israel's defense minister also vowed to impose a total siege on Gaza.

YOAV GALLANT, Israeli Defense Minister (through translator): There will be no electricity, no food, no water, no fuel.

Everything will be closed.

We're fighting against human animals, and we're acting accordingly.

LEILA MOLANA-ALLEN: The Israeli military has called upon some 300,000 reservists, possibly pointing to a major ground offensive in the days to come.

Major Ben Wahlhaus is a spokesman with the Israel Defense Forces.

MAJ. BEN WAHLHAUS, Spokesperson, Israel Defense Forces: We have cleared the Southern Israel from her muscles militants, and now our highest priority is to stop the attacks coming out from Gaza.

While this is going on, for two days, absolutely nonstop rocket barrages towards Israeli cities, population centers indiscriminately fired.

So, all options are on the table now in order to achieve that aim.

LEILA MOLANA-ALLEN: Today, the contested city of Jerusalem was also under threat.

Air sirens blasted across the city as another barrage of Hamas' rockets rained down.

Aryeh Myers is a front-line worker with Magen David Adom, Israel's national emergency service.

For the past three days, he and his team have been responding to the attacks and treating injured civilians.

He says the strikes are indiscriminate.

ARYEH MYERS, Senior Paramedic, Magen David Adom (through translator): Several of our ambulances have come under fire.

It's something that I have never experienced.

I have been a paramedic for over 20 years.

LEILA MOLANA-ALLEN: Hamas' offensive thus far has focused mostly on Southern Israel.

Through the night, rockets from Gaza continued to fly over the border into Israel.

In the city of Ashkelon this morning, emergency workers cleared the rubble after a rocket hit this apartment building, engulfing nearby cars in flames and destroying building facades, including Ofir Shasha's.

OFIR SHASHA, Ashkelon Resident (through translator): We heard sirens we heard explosions without a break.

We heard bombing.

The whole house was shaking.

Thank God nothing happened to us.

LEILA MOLANA-ALLEN: But hundreds were killed over the weekend in the nearby kibbutz of Re'im after Hamas militants attacked an outdoor rave packed with thousands of young people.

What was supposed to be a celebration of life became a massacre.

This young reveler filmed a video as she tried to escape the bullets.

Palestinian militants took dozens of Israelis hostage and shot at anyone they saw.

Hamas' armed wing said late today it will begin executing hostages if Israeli bombardments continue without warning.

But Israel's Foreign Ministry said negotiations are not on the table.

LIOR HAIAT, Spokesperson, Israeli Ministry of Foreign Affairs: We're not negotiating with anyone at this time.

We are in a war.

And I think that this is not the time for negotiation and mediation.

GEOFF BENNETT: That was Leila Molana-Allen reporting tonight in Tel Aviv.