AMNA NAWAZ: Welcome to the "News Hour."

It is the deadliest day in the Middle East since the October 7 terror attacks.

Lebanese authorities say Israeli airstrikes killed nearly 500 people and wounded more than 1,600.

GEOFF BENNETT: Israel said it struck 1,100 targets where Iran-backed Hezbollah hid weapons in Lebanon, including thousands of rockets and missiles in a stash often fired at Israel.

The tensions have led the U.S. Defense Department to send additional troops to the region.

Nick Schifrin starts our coverage.

NICK SCHIFRIN: In towns across southern and Eastern Lebanon today, at more than 1,000 sites, an avalanche of airstrikes.

Lebanese across the region said today felt like the beginning of war.

Thousands of families fled, cramming everyone they could fit into every vehicle they could find, even those shattered by shrapnel.

AHMED, Southern Lebanon Resident (through translator): Strikes, warplanes, destruction.

No one is left there.

Everyone has fled.

We took our belongings and left.

NICK SCHIFRIN: Since October the 8th, Hezbollah has fired thousands of rockets into Israel, including yesterday outside Israel's third largest city.

And Israel says its goal is to return some 60,000 residents to now empty Northern Israeli towns.

BENJAMIN NETANYAHU, Israeli Prime Minister (through translator): I promised that we would change the security balance, the balance of power in the north.

That is exactly what we are doing.

We're destroying thousands of missiles and rockets directed at Israeli cities and Israeli citizens.

NICK SCHIFRIN: And Israel expanded its targets today, warning residents to leave any homes with weapons in the Beqaa Valley, where Hezbollah was founded decades ago near the border with Syria.

REAR ADM. DANIEL HAGARI, Spokesperson, Israeli Defense Forces: We advise civilians from Lebanese villages located in and next to buildings and areas used by Hezbollah for military purpose, such as those used to store weapons, to immediately move out of harm's way for their own safety.

NICK SCHIFRIN: Israel said the targets were Hezbollah, but Lebanese officials say Israel also struck hospitals, medical centers and other civilian infrastructure.

It is a dangerous, violent escalation one day after Hezbollah leaders promised their own escalation.

NAIM QASSEM, Hezbollah Deputy Secretary-General (through translator): We don't need to make threats, and we won't specify how we will respond to aggression.

We have entered a new phase titled open-ended battle of reckoning.

NICK SCHIFRIN: But over the last week, it's been Hezbollah that's faced unprecedented attacks, their walkie-talkies and pagers turned into bombs, injuring thousands and killing nearly 40.

And on Friday, an Israeli airstrike in Southern Beirut killed the founder of Hezbollah's special forces unit, but also dozens of civilians, who have faced the brunt of the violence, the U.N. said today.

IMRAN RIZA, U.N. Deputy Special Coordinator For Lebanon: What we have seen over the last week has been dramatic, has been dramatic.

The consequences on civilians has been huge.

NICK SCHIFRIN: Today in Washington, for at least the fifth time in the last week, President Biden urged restraint.

JOE BIDEN, President of the United States: My team is in constant contact with their counterparts, and we're working to de-escalate in a way that allows people to return to their homes safely.

NICK SCHIFRIN: But if Israel's hope is that Hezbollah chooses diplomacy, analysts say this week's attacks will produce the opposite effect, and is already leading to the very escalation from both sides the U.S. has been trying to prevent.

For the "PBS News Hour," I'm Nick Schifrin.