GEOFF BENNETT: Welcome to the "NewsHour."

Fierce fighting between Israelis and Palestinians continues tonight, as airstrikes and artillery pound Gaza after Saturday's Hamas invasion of Southern Israel.

The death tolls continue to mount.

More than 1,000 Israelis and 900 Palestinians have been killed in four days of attacks and counterstrikes.

Among the dead are 14 Americans killed by Hamas.

Still other Americans are now confirmed held hostage by the terrorists in Gaza.

Again tonight from Israel, special correspondent Leila Molana-Allen starts our coverage.

LEILA MOLANA-ALLEN: Wails of loved ones mingle with the scream of sirens and the constant echoing boom of incoming and outgoing rockets.

Families along both sides of the Gaza border barely have time to bury and mourn their dead as they face the threat of yet more violence and death.

Here in the Israeli town of Sderot, 29-year-old policewoman More Shkouri was one of eight people from this community buried today, five of them police officers.

When Hamas militants stormed the police station here on Saturday, she was shot by a sniper as she tried to seek shelter.

WOMAN (through translator): I didn't have a chance to say goodbye to you.

The last words I heard from you were screaming in terror.

LEILA MOLANA-ALLEN: As families mourn, the Israel Defense Forces stepped up their campaign to eradicate the threat from Hamas.

To help stop the terror attacks by land and air, the U.S. promised Israel unconditional support and pledged more munitions and the movement of an aircraft carrier battle group closer to Israel, in addition to the $3 billion a year it already sends in military aid.

Today, President Biden confirmed that American citizens are among those held hostage by Hamas, and again emphasized U.S. support for Israel.

JOE BIDEN, President of the United States: For 75 years, Israel has stood as the ultimate guarantor of security of Jewish people around the world so that the atrocities of the past could never happen again.

And let there be no doubt: The United States has Israel's back.

We will make sure the Jewish and democratic State of Israel can defend itself today, tomorrow, as we always have.

It's as simple as that.

LEILA MOLANA-ALLEN: On the ground, Israelis are focusing on more immediate battles.

At the border area's biggest hospital in Ashkelon, doctors haven't slept for days trying to save the wounded who lived long enough to make it there.

DR.

ROB LOBEL, Ashkelon Barzilai Hospital: Being the closest hospital to Gaza, we have been trained by the events.

We have been treating 500 -- more than 550 injured.

That's an incredible number.

I mean, we are used to mass-casualty events.

We are prepared for mass-casualty events.

A big mass casualty event is considered 30 injured.

LEILA MOLANA-ALLEN: Dr.

Rob Lobel is from a village less than a quarter-of-a-mile from the Gaza border.

After spending hours hiding from the Hamas fighters rampaging through his hometown on Saturday, he headed straight to work and has since been working 20-hour shifts along with his colleagues.

DR.

ROB LOBEL: Since Sunday, I think since Sunday morning, I'm here.

LEILA MOLANA-ALLEN: So you have been treating some of your own friends and neighbors as well?

DR.

ROB LOBEL: Yes, absolutely, absolutely, many of them.

LEILA MOLANA-ALLEN: He believes his community will rebuild, but some things will never be the same.

DR.

ROB LOBEL: The main thing that we have lost, especially people who live in the surrounding area of Gaza, is our sense of security, maybe our illusion of security.

LEILA MOLANA-ALLEN: Many here fear there is worse yet to come.

The Israel Defense Forces say they have now recaptured the entire border with Gaza, but we can still hear some gunfight in the background here in the town of Sderot.

There's been an evacuation order, which suggests to some people that a ground invasion is planned.

But as some residents start to clear out of town, others are refusing to budge.

VLADIMIR KLAIDERMAN, Sderot Resident (through translator): No, they can't tell me to go away.

LEILA MOLANA-ALLEN: Gina Halford says she trusted her government to protect them, and it didn't.

So why would she listen now?

GINA HALFORD, Sderot Resident (through translator): Ben-Gvir is Satan.

Netanyahu is even worse.

And we're paying the price here.

Terrorists in Sderot slaughtered soldiers.

Where is my prime minister?

Where is my country?

I'm not going anywhere.

LEILA MOLANA-ALLEN: Just moments after we left Sderot, another gun battle broke out between security forces and Hamas militants.

And even as residents of these embattled border towns make the choice whether to stay or go, facing even more violence to come, the rockets fall without end.

In these Israeli towns just a few miles from the border with Gaza, when the sirens sound, there's less than 15 seconds to take cover before the rockets begin to fall.

There are reinforced shelters spread all around, but, often, there just isn't time to get to one.

The rocket bombardments coming from Gaza are so frequent now that Israel's state-of-the-art defense and warning system can't handle them all.

Today, many fell with no warning at all.

Just across the border in Gaza, civilians have no shelters at all.

And, today, Israel's rage intensified.

The Israeli military said it all but destroyed the district of Rimal, an administrative hub for the Hamas government.

And in Khan Yunis, bombs reportedly targeted the house of a Hamas leader.

Waves of airstrikes continue to pound the Strip neighborhood by neighborhood and, in the process, razed entire districts to the ground.

PLESTIA ALAQAD, Palestinian Journalist: That's the view from the balcony.

LEILA MOLANA-ALLEN: Palestinian journalist Plestia Alaqad shared this video from her apartment in Gaza, the view completely shrouded in smoke.

Streets like this one are deserted, coated in gray ash and lined with small mountains of crushed concrete.

SHAMES OUDA: The situation is very scary.

LEILA MOLANA-ALLEN: "NewsHour" producer Shames Ouda spoke to us from the ground there hours after a bombardment shredded the area.

SHAMES OUDA: We're standing near a public building that was -- been attacked this morning.

More than 15 people was killed in this building.

And two journalists was filming here, was killed during this attack.

As you see, all the building was destroyed.

LEILA MOLANA-ALLEN: The U.N. reported that more than 187,000 Gazans have now been displaced, fleeing their homes near the border and moving towards the sea, where a naval blockade awaits.

Many have nowhere left to go.

SAMAH ABO LATIFA, Gaza Resident (through translator): We had fled to escape from death.

We came to find death.

If we stayed in our houses, we die.

If we go on the streets, we die.

LEILA MOLANA-ALLEN: In the quiet between strikes, Palestinians carried the dead, honoring them with funeral processions through the streets of Gaza City.

The ripple effects of this war are being felt across the Middle East.

Israel has deployed tanks near the border with Lebanon, where residents in the Hezbollah-controlled south fear violence could escalate.

And there are concerns of possible escalation between Israel and Iran.

Iran's supreme leader today denied it helped plan Hamas' attack, but praised the operation.

AYATOLLAH ALI KHAMENEI, Supreme Leader of Iran (through translator): Supporters of Israel have made false statements, including that the Islamic Iran is behind this movement.

They are wrong.

But, of course, we defend Palestine.

We are proud of them.

LEILA MOLANA-ALLEN: As politicians vie for power, the violence rages on, and people on both sides of the border feel they have nowhere left to go.

After a lifetime of war, all they can do is sit and wait as another ramps up on their doorstep.

And, Geoff, that's what's so strange and terrifying about this situation on the ground.

People on both sides of the border, they're already at war, under bombardment every day.

But what they're all afraid of, what they're all talking about is the next bigger war that they all think is coming.

We saw today that first shipment of promised U.S. munitions turning up.

And the Israeli Defense Forces, they're ramping up.

They're calling up reservists to 360,000 people today.

GEOFF BENNETT: And, Leila, you and your team spent the day at the center of the strike zone, as I understand it.

Tell us what you saw.

LEILA MOLANA-ALLEN: We did.

And the way things work here, of course, the Gaza Strip is a long strip along the south of Israel.

And as you get closer and closer to it, these very large towns and cities that have hundreds of thousands of people living in them, there are seconds within which, if rockets are launched from Gaza, you have time to take shelter.

And in the closest places, that's under 10 seconds.

Now, we were down there all day in various towns.

People were trying to bury their dead.

There were multiple funerals.

People are also out in the streets trying to help feed people who've lost their homes, who've been evacuated.

And all the while, every 10 to 15 minutes, the sirens go off.

And you have that time to take shelter.

There are lots of shelters on the Israeli side of the border.

The problem is that, it's such a rapid amount of time, you often can't get to them.

And when you got really close to the border today, sometimes, those systems weren't even working because they're so overwhelmed, so many rockets coming in.

You saw there in that piece several times today we had rockets coming straight over our heads, had to hit the ground with absolutely no warning, and they're hitting very close by.

GEOFF BENNETT: After four days of heavy airstrikes, what's the situation like for Gazans?

LEILA MOLANA-ALLEN: The situation for Gazans is absolutely dire.

And humanitarian organizations have been calling out, begging today for humanitarian corridors to be created.

Now, people aren't really doubting in those organizations that Israel does need to take action, because, of course, what -- the Hamas attacks this weekend were unprecedented and something must be done.

They can never allow this to happen again.

But how they do it is the problem.

Gaza is such a densely packed, less-than-30-mile strip, civilians everywhere.

Many of the buildings that Hamas use have civilians in them.

And they really have nowhere to go.

They have been fleeing from the border side, where rockets are coming in constantly.

Going towards the sea, there's a naval blockade on that side, where there's artillery fire coming in.

So, they do have nowhere to go.

And the crossing into Egypt, which was the one place, the Rafah Crossing, that they could actually go to try and get humanitarian assistance in an emergency if they were allowed through, was hit yesterday, and so that's closed too.

Currently, there is no way for more than two million people to get out of this place, and we are looking probably at a military incursion very soon on the ground.

People are absolutely terrified.

GEOFF BENNETT: Leila, the last time you were there to report in early July, it was young people and soldiers protesting against the government.

Now they're at war.

How is that dynamic playing out?

LEILA MOLANA-ALLEN: Well, that's sort of so interesting.

All these young people who say that this right-wing government is doing things that Israelis, liberal Israelis don't want, and that they're all having to serve in the IDF, and they don't want their kids to have to die for a cause they don't believe in, everyone has rallied because they are now at war, but many people saying that right-wing government is the reason this has happened, that they have moved so many soldiers into the settlement areas in the West Bank, away from where they should have been protecting things on the Gaza Strip.

And that's why they're so angry that this wasn't foreseen, that the Israeli intelligence services missed this massive operation that has killed nearly 1,000 Israelis now.

GEOFF BENNETT: Leila Molana-Allen reporting tonight from Tel Aviv.

Leila, our thanks to you and your team there.

GEOFF BENNETT: The war between Israelis and Palestinians has upended President Biden's foreign policy efforts.

To explain how the administration is responding to the attacks, we're joined now by our White House correspondent, Laura Barron-Lopez.

So, Laura, President Biden gave this impassioned condemnation of Hamas' terrorist attacks during his remarks today from the White House.

What was his message?

LAURA BARRON-LOPEZ: As you said, Geoff, he forcefully condemned Hamas' attack and stated unequivocally that the United States and his administration stand behind Israel, the Israeli people, the Jewish people.

The president also made clear, distinguishing between Hamas' horrific actions, as well as the impact that this has had on Palestinian civilians.

JOE BIDEN, President of the United States: There is no justification for terrorism.

There is no excuse.

Hamas does not stand for the Palestinian people's right to dignity and self-determination.

Its stated purpose is the annihilation of the state of Israel and the murder of Jewish people.

They use Palestinian civilians as human shields.

Hamas offers nothing but terror and bloodshed with no regard to who pays the price.

LAURA BARRON-LOPEZ: Another notable message from the president today, Geoff, was that he, as well as his administration officials, compared Hamas' attacks to the very worst of ISIS terrorism.

GEOFF BENNETT: What more is the White House doing to aid and support Israel and to find those missing Americans?

LAURA BARRON-LOPEZ: They're working with Israel, as well as other partners, to try to find the missing Americans and recover the hostages.

That includes intelligence sharing.

And Jake Sullivan, the national security adviser, told us in the White House briefing today that there are at least 20 missing.

Not all of those 20 missing Americans, though, are necessarily hostages, and that we do not know at this time the number of American hostages that Hamas has taken.

In addition to aiding Israel, the White House is also sending ammunition, air defense, and Sullivan said that they are trying to come up with as many contingency plans as possible for scenarios in case this conflict escalates.

GEOFF BENNETT: I was told by a U.S. official today that U.S. officials and Israeli officials are talking about this idea of creating safe passage for some Gaza civilians.

What more on that front did you pick up in your reporting today?

LAURA BARRON-LOPEZ: So the president stressed today, Geoff -- that he used the term abiding by -- quote -- "law of war."

And so that's a message that he was sending.

It's also something that he talked about in his conversation today with Prime Minister Netanyahu.

And Jake Sullivan said that they also talked about making sure that, when and as Israel takes action against Gaza and against Hamas, that civilians are not deliberately attacked.

And so that's something that the president has been talking to Netanyahu about.

I also asked Sullivan about the thing that you mentioned, Geoff, which was whether or not the administration is trying to help civilians find passages out of Gaza.

And he didn't give specifics about any types of border crossings that they might be opening up.

But he did say that it is a primary focus of the administration and something that they're working towards.

GEOFF BENNETT: And, Laura, there's a role for Congress here too.

What's the administration asking lawmakers on Capitol Hill to do about this?

LAURA BARRON-LOPEZ: A big focus of the administration's, Geoff, is to see former Treasury Secretary Jack Lew confirmed to be the Israel ambassador, the ambassador to Israel for the U.S. And a White House official told me that they are in close touch with senators to try to make sure that confirmation happens as quickly as the Senate returns.

They also are going to be seeking additional funding for Israel.

But the White House today did not say whether or not they were going to try to tether that additional Israel aid security funds to, again, funding that they want to see go to Ukraine.

They are going to renew that Ukraine request, but they didn't say whether or not they were going to try to push it all as one package.

GEOFF BENNETT: Laura Barron-Lopez, thanks so much for sharing that reporting with us.

LAURA BARRON-LOPEZ: Thank you.