Israel ordered a “complete siege” of the Gaza Strip on Monday as it retaliated for the largest and deadliest incursion into its territory in decades, while Hamas threatened to respond to the Israeli bombing campaign by executing civilians its fighters took hostage in Israel.
Defense Minister Yoav Gallant of Israel said that “no electricity, no food, no water, no fuel” would be allowed into Gaza, the crowded and impoverished coastal territory that is already under a 16-year blockade by Israel and Egypt. Israeli warplanes struck hundreds of sites in Gaza, which is controlled by the militant group Hamas, including mosques and a marketplace, while Israeli troops battled to regain control of towns overrun on Saturday by Hamas gunmen.
More than 900 people have been killed in Israel, the Israel Defense Forces said. More than 2,600 have been wounded since the incursion began early Saturday, and Hamas gunmen were holding about 150 hostages, the Israeli government said. The spokesman for Hamas’s military wing, Abu Obeida, said the group would execute a civilian hostage every time an airstrike hit Gazans “in their homes without warning.”
At least 687 Palestinians were killed and at least 3,726 injured, the authorities in Gaza said. The death toll is believed to include not only the casualties in Gaza, but also some of the assailants who were killed in the attack on Israel, though it was not immediately clear how many.
Israel mobilized 300,000 military reservists, an enormous number for a country of 9 million people, amid signs that it could be preparing for a major ground invasion of Gaza and the possible opening of another front against the Lebanese Shiite group Hezbollah in the north.
In a televised address on Monday night, Prime Minister Benjamin Netanyahu of Israel, who has warned of a long war ahead, vowed to “eliminate” Hamas. Mr. Netanyahu, who leads the most right-wing government in his nation’s history, called on the opposition to “immediately establish a national emergency government without preconditions.”
Lt. Col. Richard Hecht of the Israel Defense Forces told reporters on Monday that the next phase of fighting would not resemble recent conflicts with Gaza, in which Palestinian groups fired rockets but claimed relatively few casualties, and Israel would respond primarily with airstrikes. “We are in a different game here,” he said. “We are at war with Hamas.”
A stunned disbelief enveloped Israel, which appeared to have been caught entirely by surprise by the attack and had gone 50 years without enduring an assault on this scale or with so many casualties. Adding to the shock were the mass hostage-takings and the fact that fighting on Israeli soil continued into a third day. Families were watching men and women who had finished their mandatory military service being called back to duty, while the names of the dead scrolled across television screens.
An Israeli airstrike on Monday devastated a busy open-air marketplace in northern Gaza’s Jabaliya refugee camp, where Gazans anticipating a long fight had flocked to stock up on food and other supplies. A Red Crescent paramedic, who was not authorized to speak to the media and requested anonymity, said 60 people were killed there.
Videos shared on social media and distributed by Palestinian news agencies showed bodies strewn amid the debris of what moments earlier had been stands selling produce and other goods. Broken concrete and twisted metal from the surrounding buildings filled the square, and people made their way through the debris, smoke and dust, looking for survivors.
“Is he dead? Is he dead?” a man was heard yelling in one video.
Israeli strikes also hit four mosques in the Shati refugee camp on Monday, according to Gaza authorities, toppling their domes and killing worshipers inside. Neighbors picked through the rubble of the Sousi mosque, where witnesses said boys had been playing soccer just outside when it was destroyed.
Israel’s military said it had carried out more than 500 airstrikes overnight, targeting operations centers of Hamas and another group, Islamic Jihad. It confirmed hitting several mosques, saying that they contained Hamas infrastructure or fighters.
The United Nations and Palestinian officials said that at least two hospitals and multiple homes had also been hit, and many Gazans said they had nowhere to go to escape the Israeli strikes.
President Biden said at least 11 U.S. citizens were confirmed killed in the Hamas attack, and an unknown number were 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 written statement.
He vowed to work with Israel “on every aspect of the hostage crisis,” including sharing intelligence and deploying experts.
Mr. Biden and the leaders of Britain, France, Germany and Italy also released a statement late Monday condemning “Hamas and its appalling acts of terrorism.”
Many other foreign nationals were reported dead, wounded or missing, including 12 Thais killed, 11 kidnapped and nine wounded, according to their government. France said two of its nationals were killed and 14 were unaccounted for.
Israel has asked the United States to supply it with more precision-guided munitions for its warplanes and more missiles for its Iron Dome air defense system, requests the Biden administration is working on, according to a U.S. official who spoke on condition of anonymity to discuss internal deliberations. A senior Pentagon official said the United States was already accelerating shipments of such weapons.
More than 100 people were killed over the weekend in a Hamas assault on an Israeli kibbutz, Be’eri, said Moti Bukjin, a spokesman for the ZAKA relief organization, which was recovering bodies there on Monday. “It was horrible work. There were killed children there,” he said, adding that there were dozens of dead militants in the town as well.
At least 109 people were killed by gunmen who swarmed into a weekend music festival at a venue in Israel three miles from the Gaza border on Saturday. But ZAKA volunteers later reported recovering an estimated 260 bodies at the site of the rave, Mr. Bukjin said. Videos show panicked concertgoers fleeing south into the desert and more than 100 abandoned vehicles on the side of the road.
Hamas’s armed wing, the Al Qassam Brigades, said four Israelis were killed in one of the Israeli airstrikes, along with the Palestinian gunmen who were holding them captive, a claim that could not be independently verified.
A new barrage of rockets fired into Israel from Gaza injured seven people on Monday, officials said, while sirens blared in Jerusalem and across central Israel. Schools remained closed and flights in and out of the country were curtailed.
Israeli leaders are concerned that Hezbollah, the powerful Lebanese militia allied with Iran, could enter the fight, and Israeli military units in the north are on high alert. Israel and Hezbollah fought a monthlong war in 2006.
Fighting escalated on Monday on that front, along Israel’s northern frontier with Lebanon, with Islamic Jihad claiming responsibility for small cross-border attacks there, a day after Hezbollah fired on Israeli posts and Israeli forces fired back. Israel’s military said on Monday that it had struck three Hezbollah posts in Lebanon, and Hezbollah said that three of its fighters had been killed. The group later said it had carried out attacks on two Israeli military barracks, using guided missiles and mortars.
It was not clear what prompted the timing of the most audacious attack Hamas has ever launched on Israel. Hamas is backed by Iran, as is Islamic Jihad, and Tehran is eager to derail a possible diplomatic deal between its two regional archenemies, Israel and Saudi Arabia. The Iranian foreign ministry denied that its government had any role in the fighting. U.S. officials said that no evidence had emerged so far of Iranian involvement, but that Iran was complicit in the attack, given its years of support for Hamas.
Israel’s chief military spokesman, Rear Adm. Daniel Hagari, declared on Monday that the army had regained control of border communities, though “there may still be terrorists in the area.” But a short time later the military said soldiers and armed militants were exchanging gunfire in Kfar Azza, an Israeli village near the border.
Colonel Hecht said in a news briefing on Monday that Israeli special forces troops were trying to dislodge militants from a civilian area.
“We thought by this morning we’d be in a better place,” he said.
Israeli rescue workers were still extracting the bodies of civilians who were killed in their homes by Hamas gunmen on Saturday.
Mr. Netanyahu warned local leaders in southern Israel to prepare for a long fight, his office said.
“I know you have been through tough and terrible things. What Hamas will go through will be tough and terrible,” he told them, according to his office. “We are already in the midst of a battle that has only just begun.”
The United Nations humanitarian agency said Israeli strikes had displaced 123,000 Gazans, and damaged water, sanitation and hygiene facilities affecting more than 400,000 people. The only power plant providing electricity to Gaza could run out of fuel in a few days, aid agencies have said.
In the north, Israel’s Home Front Command instructed the residents of 28 towns and villages near the border with Lebanon to go to bomb shelters and other protected spaces. The residents were told to take food, water, mattresses, and blankets, signaling that they may need to stay there for a while.
The Lebanese Army said Israeli planes and artillery struck near the towns of Dhayra and Aita al Shaab close to the border with Israel earlier on Monday. The military instructed Lebanese civilians “not to go to areas adjacent to the border for the sake of their safety.”
Isabel Kershner reported from Jerusalem, Aaron Boxerman from London and Hiba Yazbek from Nazareth, Israel. Reporting was contributed by Raja Abdulrahim, Ameera Harouda, Edward Wong, Farnaz Fassihi, Peter Baker, Cassandra Vinograd, Ronen Bergman, Sui-Lee Wee, Eric Schmitt, Euan Ward and Tiffany May.