Israeli Prime Minister Benjamin Netanyahu threatened Gaza with a "long and difficult" war as he told the nation that the military has opened a "second stage" in the conflict by sending ground forces into the coastal strip and expanding attacks from the ground, air and sea.

Casting the war on Palestinians as a fight for his country's very survival, he warned that the assault would intensify ahead of a broad ground invasion into the territory.

"There are moments in which a nation faces two possibilities: to do or die," Netanyahu said. "We now face that test and I have no doubt how it will end: We will be the victors. We will do and we will be the victors."

The bombardment, described by Gaza residents as the most intense of the war, knocked out most communications in the territory and largely cut off the besieged enclave's 2.3 million people from the world.

The military released grainy images showing tank columns moving slowly in open areas of Gaza, many apparently near the border, and said warplanes bombed dozens of Hamas tunnels and underground bunkers, a key target in Israel's campaign.

The escalation ratcheted up domestic pressure on Israel's government to secure the release of dozens of hostages seized in the Oct. 7 Hamas incursion.

Desperate family members met with Netanyahu on Saturday and expressed support for an exchange for Palestinian prisoners held in Israel, a swap floated by the top Hamas leader in Gaza.

Netanyahu told the nationally televised news conference that Israel is determined to bring back all the hostages, and maintained that the expanding ground operation "will help us in this mission." He said he couldn't reveal everything that is being done due to the sensitivity and secrecy of the efforts.

"This is the second stage of the war, whose objectives are clear: to destroy the military and governmental capabilities of Hamas and bring the hostages home," he said in his first time taking questions from journalists since the war began.

He didn't address calls for a cease-fire, but in a speech peppered with references to centuries of Jewish history and military conflicts, made clear his view that Israel's future depends on its success against "enemy" forces.

"Our heroic soldiers have one supreme goal: to destroy the murderous enemy and ensure our existence in our land. We have always said, 'Never again,'" he said. "'Never again' is now."

Netanyahu also acknowledged that the Oct. 7 "debacle," in which more than 1,400 people were killed, would need a thorough investigation, adding that "everyone will have to answer questions, including me."

The Israeli military said it was gradually expanding its ground operations inside Gaza, while stopping short of calling it an all-out invasion.

"We are proceeding with the stages of the war according to an organized plan," said the chief military spokesman, Rear Adm. Daniel Hagari. The comments hinted at a strategy of a staged escalation, instead of a massive and overwhelming offensive.

Early in the war, Israel amassed hundreds of thousands of troops along the border. Until now, troops had conducted brief nightly ground incursions before returning to Israel.

The Palestinian death toll in Gaza rose Sunday to just over 8,000 people since the war began, according to the Gaza Health Ministry. Most of those killed have been women and minors, the ministry said.