(GAZA CITY) -- Israel hit Gaza with a series of "extensive strikes" overnight Tuesday, vowing to open the "gates of hell" because Hamas has not released the remaining hostages. At least 404 Palestinians were killed in the strikes, according to the Gaza Ministry of Health.
Israeli Foreign Minister Gideon Saar said Tuesday the operation in Gaza is "not a one-day operation."
"We will continue the military campaign in the coming days,” Saar said, speaking to American pro-Israel lobby group AIPAC, on Tuesday. "The Americans were informed before the attack and supported it because justice is on our side."
Israeli Prime Minister Benjamin Netanyahu and Defense Minister Israel Katz said the Israel Defense Forces are targeting Hamas terrorists throughout the region.
"Israel will, from now on, act against Hamas with increasing military strength," Netanyahu's office said in a statement on Tuesday.
The IDF announced a second wave of airstrikes took place in the early afternoon local time. Among the targets attacked were terrorist cells, launch sites, weapons and additional military infrastructure used by the terrorist organizations to plan and carry out terrorist acts, and which posed a threat to IDF forces and Israeli citizens, according to the IDF.
The first round of strikes targeted areas in Gaza including Rafah, Khan Younis, Deir al-Balah, Nuseirat, Al-Bureij, Al-Zaytoun, Al-Karama and Beit Hanoun. The IDF's Arabic spokesperson issued a broad evacuation order covering the entire perimeter of Gaza. Residents were warned to "evacuate immediately to the known shelters in western Gaza City and those in Khan Younis."
Of the Palestinians killed overnight, 174 were children and 89 were women, according to the ministry. The human toll in Gaza had risen steadily throughout the morning, the ministry said in a series of updates. At least 562 others were injured, the ministry said.
Doctors Without Borders said it has received dozens of killed and injured at sites across Gaza.
"We woke up, at around 2am local time, to 20 minutes of airstrikes and heavy artillery, just like the past 15 months of war. We are appalled and outraged by these new unacceptable massacres of civilians," said Claire Nicolet, Doctors Without Borders's head of emergencies.
"Tonight we returned to fighting in Gaza due to Hamas' refusal to release the hostages and threats to harm IDF soldiers and Israeli communities," Katz said in a statement.
"If Hamas does not release all the hostages, the gates of hell will open in Gaza," he added.
An Israeli official told ABC News the preemptive offensive will continue "as long as necessary," and will "expand beyond air strikes."
The Saudi Ministry of Foreign Affairs condemned the "resumption of aggression against the Gaza Strip and their direct shelling of civilian areas, with no regard for international humanitarian law."
The Egyptian Foreign Ministry also issued a statement saying it "strongly condemns" the Israeli airstrikes of Gaza, which constitute a "blatant violation" of the ceasefire and represents a "dangerous escalation. That threatens to have severe consequences for the stability of the region."
The strikes targeted Hamas' mid-ranking military commanders, leadership officials and infrastructure, the official said.
"The IDF is prepared and spread out in all arenas, both in personnel manning the borders and the Aerial Defence Array," the official added.
A missile launched from Yemen was intercepted by the Israeli Air Forces prior to crossing into Israeli territory, the IDF said in a statement. Red alert sirens were activated in several parts of central and southern Israel around 7:00pm local time.
Netanyahu and Katz said the changes to the IDF's defensive guidelines come after Hamas "rejected all offers" on a conclusive hostage deal with Steve Witkoff, the U.S.'s special envoy to the Middle East.
Hamas said in a statement Tuesday that overturning the ceasefire agreement and the series of strikes put "the prisoners in Gaza at an unknown fate."
White House press secretary Karoline Leavitt said in an appearance on Fox News that the Trump administration was consulted by Israeli officials on their decision to strike Gaza.
Earlier this month, President Donald Trump took to his social media to threaten Hamas with a "last warning" about the remaining hostages.
Trump wrote on Truth Social on March 7 that "it will be OVER" for Hamas if it does not comply.
"I am sending Israel everything it needs to finish the job, not a single Hamas member will be safe if you don't do as I say," he added.
Witkoff reiterated the president's threat at the time, saying, "I wouldn't test President Trump."
Fifty-nine hostages are believed to remain in Gaza -- 24 of whom are presumed to be alive. Edan Alexander is the last American-Israeli hostage to remain alive in captivity.
ABC News' Dana Savir and Guy Davies contributed to this report.
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