GAZA CITY, Gaza Strip (AP) — Israeli aircraft, tanks and naval gunboats pounded the Hamas-ruled Gaza Strip and rocket salvoes thudded into southern Israel on Thursday as terrified residents on both sides of the frontier holed up at their homes in anticipation of heavy fighting on the second day of Israel's offensive against the Palestinian militants.

The operation, launched in response to several days of rocket fire from the coastal territory, was Israel's most intense attack on Gaza since its full-scale war there four years ago.

It started with the assassination Wednesday of Hamas' top military commander, deepening the instability gripping the Mideast. Israel's already strained relations with Egypt's new Islamist government frayed even further as Cairo recalled its ambassador in response to the Israeli military operation.

Just days earlier, Israel was drawn into Syria's civil war for the first time, firing missiles into its northern neighbor for the first time in four decades after stray mortar fire landed in Israeli-occupied Syrian territory.

The assassination of Hamas mastermind Ahmed Jabari was followed by a wave of Israeli airstrikes on more than 100 militant targets. The air attacks continued steadily into early Thursday, targeting the armed group's training facilities and rocket launchers.

Ten Palestinians, including two young children and seven militants, were killed Wednesday and more than 93 were wounded. Early on Thursday, Israel targeted a motorcycle carrying a rocket squad, killing one militant and wounding two, a Palestinian health official said. The Israeli military had no immediate confirmation of the report.

Tank shells and naval gunfire backed up the air onslaught. Few in the territory's largest urban area, Gaza City, came out following the call for dawn prayers, and the only vehicles plying the streets were ambulances and media cars.

One of the airstrikes Wednesday destroyed a two-story house, sending rubble flying within a radius of about 500 meters (yards). It shattered windows on nearby buildings, collapsed walls, knocked down a tree and cut electricity wires and telephone cables

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Wajdi Ali, a 52-year-old teacher who lives a couple of buildings down the street, said the explosion was so powerful it threw him across his living room.

"By killing Jabari, Israel has cocked the trigger and fired at itself," he said. "No one knows when this dark chapter is going to end. I am sure that dark days await us, and them as well."

Gaza schools were ordered closed until the operation ends, and most of the territory's 1.6 million people were expected to hunker down close to home, venturing out only to buy food, fuel and other basic supplies. 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 that the Hamas fighters and other militant factions, undeterred by the air attacks, bombarded southern Israel with more than 70 rockets after the operation began. Israel's newly deployed Iron Dome missile defense system, developed as a response to the short-range rockets from Gaza, intercepted two dozen of them, military spokeswoman Lt. Col. Avital Leibovich 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 shut down. 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."

Israel said Wednesday's airstrikes were the beginning of a broader operation against the Islamic militants and that a ground invasion was a strong possibility in the coming days if Hamas didn't rein in the rocket fire. The military said it destroyed dozens of the militants' most potent rockets — the Iranian-made Fajr, which is capable of striking Israel's Tel Aviv heartland — as well as shorter-range rockets. In all, the military estimated Hamas had 10,000 rockets and mortars in its arsenal before the military operation began.

In a nationwide address, Prime Minister Benjamin Netanyahu said Israel could no longer stand repeated attacks on its southern towns. Days of rocket fire have heavily disrupted life for some 1 million people in the region, canceling school and forcing residents to remain indoors.

"If there is a need, the military is prepared to expand the operation. We will continue to do everything to protect our citizens," Netanyahu declared late Wednesday.

The Israeli military was cleared to call up special reserve units — a sign the operation might broaden.

For the past four years, Israel and Hamas have largely observed an informal truce. But in recent weeks, the calm has unraveled in a bout of rocket attacks from Gaza and retaliatory Israeli airstrikes. From Israel's perspective, Hamas escalated the situation with two specific attacks in recent days: an explosion in a tunnel along the Israeli border and a missile attack on an Israeli military jeep that seriously wounded four soldiers.

Earlier this week, Israeli defense officials warned they were considering resuming their controversial practice of assassinating senior militants. Wednesday's killing of Jabari was an indication they were serious. Israel has refrained from such attacks, which have drawn international condemnations, since its January 2009 offensive in Gaza.

Hamas officials had brushed off the Israeli threats, and Jabari, contrary to form, was driving in broad daylight when his vehicle was hit.

The Hamas military chief had long topped Israel's most-wanted list, blamed for masterminding a string of deadly attacks that including a bold, cross-border kidnapping of an Israeli soldier in 2006. He also was believed to be a key player in Hamas' takeover of Gaza in 2007 from a rival Palestinian faction, the Western-backed Fatah movement.

The Israeli military released a black-and-white video of the Jabari airstrike, showing a sedan moving slowly along a road before going up in flames in an explosion so powerful that a large chunk of the vehicle flew high into the air.

Crowds of people and security personnel rushed to the scene of the strike, trying to put out the fire that had engulfed the car and left it a charred shell. Plumes of black smoke wafted into Gaza City's skies following other airstrikes. Ambulance sirens blared as people ran in panic in the streets and militants fired angrily into the air.

Outside the hospital where Jabari's body was taken, thousands of Gazans chanted "Retaliation!" and "We want you to hit Tel Aviv tonight!"

"I was sitting on my bed with my grandson when suddenly the wall collapsed on both of our heads," said Mahmoud Bana, a 62-year-old man who was slightly wounded along with his 11-year-old grandson. "We don't know what happened but we know it is going to be a few hard days ahead."

In a statement, Hamas' prime minister, Ismail Haniyeh, eulogized Jabari and vowed revenge.

"We mourn our late leader who walked the path of jihad while he knew the end, either victory or martyrdom," Haniyeh said. "There is no fear among our people and our resistance, and we will face this vicious attack."

Advocates say targeted killings are an effective deterrent without the complications associated with a ground operation such as civilian and Israeli troop casualties, and that they also prevent future attacks by removing the masterminds. Critics say they amount to extrajudicial killings and invite retaliation by militants and encourage them to try to assassinate Israeli leaders.

During a wave of suicide bombings against Israel a decade ago, the country employed the tactic to eliminate the upper echelon of Hamas leadership.

Hamas accused Netanyahu of launching Wednesday's operation to win votes in the Jan. 22 parliamentary election. But major Israeli parties, including the dovish opposition, all lined up behind Netanyahu.

Still, the region has changed greatly since the Gaza offensive four years ago. Neighboring Egypt is now governed by Hamas' ideological counterpart, the Muslim Brotherhood.

Israel and Egypt signed a peace accord in 1979. Relations, never warm, deteriorated after longtime Egyptian President Hosni Mubarak was ousted in a popular uprising last year. The Jabari assassination threatened to further damage those fraying ties.

On its official Facebook page, Egypt's Freedom and Justice Party, which is the Muslim Brotherhood's political arm, called Jabari's assassination a "crime that requires a quick Arab and international response to stem these massacres against the besieged Palestinian people in the Gaza Strip."

It accused Israel of trying to "drag the region toward instability."

In Washington, the United States lined up behind Israel. "We support Israel's right to defend itself, and we encourage Israel to continue to take every effort to avoid civilian casualties," said State Department spokesman Mark Toner.

President Barack Obama spoke with Netanyahu and the two men agreed Hamas needs to stop its attacks on Israel to allow tensions to ease, the White House said.

Obama spoke separately to Egyptian President Mohammed Morsi, given Egypt's central role in preserving regional security, the White House said. The two men agreed on the need to de-escalate the conflict as quickly as possible.

U.N. Secretary-General Ban Ki-moon called for calm and urged both sides to respect international humanitarian law.

On Wednesday night, the U.N. Security Council met behind closed doors to consider an Egyptian request for an emergency meeting on Israel's military action in Gaza. The Palestinians asked the council to act to stop the operation.

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Teibel reported from Jerusalem. Additional reporting from Sarah El Deeb in Cairo and Bradley Klapper in Washington.