Israel said Jabari's assassination was the start of a broader offensive, launched after days of rocket fire from the coastal territory. It was Israel's most intense attack on Gaza since a full-scale invasion four years ago, also in response to rocket fire.
Despite the similarities, much has changed since then. Hamas has beefed up its arsenal with more powerful and far-reaching missiles. Israel, meanwhile, has deployed a first-of-its-kind system that shoots down incoming rockets. Officials say the "Iron Dome" system is believed to have a roughly 80 percent success rate.
Israel also faces a much-changed region. Following a popular uprising last year, Egypt is now governed by the Muslim Brotherhood, which has close ties with Hamas. Egypt's new Islamist government has so far honored a 1979 peace deal with Israel. But it is far cooler to Israel than ousted President Hosni Mubarak was.
In an initial protest, Egypt recalled its ambassador to Israel on Wednesday. Egypt's Foreign Minister Mohammed Kamel Amr also spoke with U.S. Secretary of State Hillary Rodham Clinton late Wednesday, asking for "immediate U.S. intervention to stop the Israeli aggression," the Foreign Ministry said in a statement.
Tensions have also heated up along Israel's northern border as the civil war in Syria has begun to spill over into the Israeli-controlled Golan Heights. Earlier this week, Israel twice fired in response to stray mortar shells that landed in the Golan.
Israelis were ordered to remain close to shelters or fortified rooms in their homes as air raid sirens wailed throughout the day. Police said two men and a woman died after a rocket struck their four-story apartment building in Kiryat Malachi. A 4-year-old boy and two babies were also wounded.
Israeli media reported that the victims had ignored orders to protect themselves.
"We lost people today who could have been with us if they had just followed instructions," said Avi Dichter, the Cabinet minister in charge of Israeli civil defense.
Hamas announced a state of emergency in Gaza, evacuating all its security buildings and deploying its troops away from their locations.
Israeli aircraft dropped leaflets on several locations in Gaza early Thursday, warning Gazans to stay away from Hamas, other militants and their facilities.
The Israeli military said Hamas fighters and other militant factions, undeterred by the air attacks, bombarded southern Israel with more than 180 rockets. The Iron Dome, meant to detect rockets headed toward populated areas, intercepted about 30 of them, the military said.
Israel declared a state of emergency in the country's south, where more than 1 million Israelis live within rocket range, instructing people to remain close to fortified areas. School was canceled in communities within a 40-kilometer (25-mile) radius of Gaza.
People living in areas along the frontier were ordered to stay home from work, save for essential services, and shopping centers were closed. Israeli police stepped up patrols around the country, fearing Hamas could retaliate with bombing attacks far from the reaches of Gaza.
Batya Katar, a resident of Sderot, a community that has been a frequent target of rocket fire, said streets were empty there.
"People won't be outside. The minute they assassinated the Hamas military chief we knew an offensive had begun. We were waiting for it, and it's about time they did it. We have the right to live like other countries in the world," she said.
Israeli officials said Wednesday that a ground invasion was a strong possibility in the coming days if Hamas didn't rein in the rocket fire. Mid-morning Thursday, there was no sign such an invasion might be beginning. But the Israeli military was cleared to call up special reserve units — a sign the operation might broaden.
The Israeli military released a series of videos showing black-and-white footage of its targets being struck: weapon depots and rocket launching pads.
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