“No electricity, no food, no fuel,” Gallant said. “We are fighting animals, and we will act accordingly.”
The move to punish Gaza for the carnage in Israel came as the death toll grew on both sides. In Israel, at least 900 people have been killed since the attacks started Saturday, local media reported. Palestinian health officials in Gaza said that 687 people have died as a result of Israeli strikes.
In a statement released Monday evening, President Biden said that “at least 11 American citizens were among those killed,” including many who had made a “second home in Israel.” That number could rise, he said, with U.S. citizens still unaccounted for.
“While we are still working to confirm, we believe it is likely that American citizens may be among those being held by Hamas,” he said.
In a televised address, Israeli Prime Minister Benjamin Netanyahu warned that Israel’s response was only just starting. He compared Hamas to the Islamic State group, which once controlled swaths of Iraq and Syria and carried out deadly attacks in Europe and North Africa.
“What we will do to our enemies in the coming days will reverberate with them for generations,” Netanyahu said.
The rhetoric from Israeli officials alarmed some observers who called it dehumanizing, while others urged restraint.
U.N. Secretary General António Guterres said Monday that he was “deeply distressed” at Israel’s plan to “initiate a complete siege of the Gaza Strip.”
Palestinian civilians are “trapped and helpless,” Guterres told reporters in New York, calling on Israel to allow continued access for relief officials and humanitarian supplies.
About 137,000 displaced people were sheltering in schools and facilities operated by UNRWA, the U.N. relief agency for Palestinians, Guterres said.
Even before the war, Hamas-led Gaza struggled under a years-long blockade. It gets most of its electricity from Israel, and its groundwater sources have been ruined by pollution and saltwater. More than 90 percent of the water in Gaza’s sole aquifer is no longer potable.
But there was no sign that Hamas was de-escalating. Air raid sirens blared in Jerusalem and Tel Aviv as the group launched salvos at the two cities, appearing to flex its ability to continue striking at the heart of Israel.
Explosions were heard in Jerusalem, alongside sonic booms, indicating the activation of Israel’s Iron Dome air defense system. Rockets also landed in southern towns, including Ashkelon.
Projectiles landed in Tel Aviv and in Jerusalem in open areas, as well as on Highway 1, the main route connecting the two cities. The country’s main airport remained open, but many carriers canceled flights.
As Israeli troops and tanks headed toward the Gaza border, Hamas fighters continued to infiltrate the border and might have entered Israeli territory, Lt. Col. Richard Hecht, a spokesman for the Israel Defense Forces, said at a news briefing Monday.
“We are still fighting. We thought this morning that we would be in a better place,” Hecht said. “We still have open areas. I can’t say that they’re not still coming in.”
Hecht said it was taking Israeli forces “more time than we thought” to repel Hamas fighters, in part because of the presence of civilians. “This is not military fighting militants. There are civilians in the midst of it. … We are doing it in a very surgical way. It is taking a lot of time.”
The Israeli military said “most” of the breach points had been secured.
Masha Michelson, deputy head of the IDF for the international media, said Israeli forces “have reestablished control of communities near the Gaza Strip … but isolated clashes continue as some Palestinian gunmen remain active.”
More than 100 people were “taken captive” by Hamas, Israeli Foreign Minister Eli Cohen told a group of foreign journalists in Jerusalem on Monday, Reuters reported.
“This is something different — unprecedented,” Hecht said. “And it’s not soldiers [being held hostage]. … It’s a grandmother, a child, a family, a girl.”
Hamas’s military wing, the Izzedine al-Qassam Brigades, threatened to execute the hostages if more civilians were killed in Gaza. In an audio message aired on the Al Jazeera news network, Qassam spokesman Abu Obeida said the executions would be recorded.
Searching for ways to describe both the scale and surprise of the Hamas attacks, Israeli officers and diplomats repeatedly compared Saturday’s raid to the Japanese attack on Pearl Harbor and to 9/11.
Lt. Col. Jonathan Conricus, an IDF spokesman, told the BBC that “this could be a 9/11 and a Pearl Harbor wrapped into one.” He called it “by far the worst day in Israeli history. Never before have so many Israelis been killed by one single thing, let alone enemy activity, on one day.”
On Monday, the Israeli rescue service Zaka said more than 100 bodies had been recovered from Beeri, a kibbutz near the Gaza border where Palestinian militants had seized control.
Inside Gaza, residents spent another terrifying night, feeling and hearing the Israeli bombardment from aircraft, artillery and ships.
The Israeli air force said Monday that it struck more than 500 Hamas and Islamic Jihad targets in Gaza overnight, including seven Hamas command centers and one used by Islamic Jihad.
Homes belonging to known Hamas leaders were leveled. At least four mosques were destroyed. Thousands crowded into schools, seeking shelter. The main hospital in Gaza City was also filled with panicked refugees, alongside the sick and wounded.
The crossing from Gaza into Egypt remained partially open Monday and was overwhelmed with people trying to flee. Internet lines were severed, electricity was sporadic, water tanks were running dry.
Most of Gaza’s fresh fruit and vegetables come from the farms along its border with Israel. With an invasion, those fields will become a war zone.
Ordinary people said they were dreading what comes next — in part because it remains unclear what Hamas wants. Spokesmen for the group have issued vague statements calling for the release of all Palestinian prisoners held by Israel.
The presence of both civilian and military hostages in Gaza greatly complicates matters.
The most high-profile previous hostage was snatched in a cross-border raid in 2006: the soldier Gilad Shalit, who was released after five years, when Israel agreed to free 1,000 Palestinian prisoners.
Hamas remained defiant. Spokesman Abdul Latif al-Qanu accused Israel of committing crimes against humanity by killing civilians and said the international community has double standards when it comes to Palestinian deaths.
“The criminal Zionist entity is trying, through the war crimes it’s committing, to rebuild its army’s spirits and its broken soldiers and to snatch the fake image after the elite Qassam’s strikes and its killing and capture of [Israel’s] army and settler herds,” he said in a statement published on the group’s Telegram channel.
Israel also faces threats from the north. Israeli soldiers killed two of five militants who crossed into Israel from Lebanon on Monday, the army spokesman announced. There was no word on the fate of the other three.
Israeli helicopter gunships were deployed to Lebanese territory, Rear Adm. Daniel Hagari, an IDF spokesman, said on X, formerly Twitter. The military reported destroying a position manned by the Lebanese militant group Hezbollah. The Hezbollah-linked al-Manar channel reported that an empty home was hit.
“We have nothing to do with this,” a Hezbollah spokesperson told The Washington Post via Telegram. “It’s not us. And we don’t know if there was an infiltration or not.”
The armed wing of Palestinian Islamic Jihad, a group active in Lebanon, Gaza and the West Bank, claimed responsibility for the attack in northern Israel on Monday. Hezbollah later confirmed that three of its members were killed by the shelling and fired a salvo of rockets toward northern Israel in response.
The incidents raised fears of a wider escalation. Israel fought a war with the militant group in 2006 that killed more than 1,000 people.
Rubin reported from Brussels, George from southern Israel, Balousha from Gaza City and Booth from London. Sarah Dadouch in Beirut, Noga Tarnopolsky in Jerusalem and Karen DeYoung in Washington contributed to this report.