Israeli warplanes retaliating for rocket fire from the Gaza Strip pounded dozens of security compounds across the Hamas-ruled territory in unprecedented waves of airstrikes Saturday, killing more than 200 people and wounding nearly 400 in the single bloodiest day of fighting in years.

Most of those killed were security men, but an unknown number of civilians were also among the dead. Hamas said all of its security installations were hit, threatened to resume suicide attacks, and sent at least 50 rockets crashing into Israeli border communities, according to the Israeli military's count. One Israeli was killed and at least six people were wounded in the rocket attacks.

With so many wounded, the Palestinian death toll was likely to rise.

The strikes caused widespread panic and confusion in Gaza, as black clouds of smoke rose above the territory, ruled by Hamas for the past 18 months. Some of the Israeli missiles struck in densely populated areas as children were leaving school, and women rushed into the streets frantically looking for their children.

Said Masri sat in the middle of a Gaza City street, close to a security compound, alternately slapping his face and covering his head with dust from the bombed-out building.

"My son is gone, my son is gone," wailed Masri, 57. The shopkeeper said he sent his 9-year-old son out to purchase cigarettes minutes before the airstrikes began and now could not find him. "May I burn like the cigarettes, may Israel burn," Masri moaned.

The offensive began eight days after a six-month truce between Israel and the militants expired. During that time, the military says, rocket and mortar squads have fired 200 projectiles at Israeli targets, and in recent days, Israeli leaders had been voicing strong threats to launch a major offensive.

Defense Minister Ehud Barak said Israel would expand the operation if necessary. "There is a time for calm and there is a time for fighting, and now is the time for fighting," he told a news conference. He did not say whether a ground offensive was planned.

Asked earlier if Hamas political leaders might be targeted next, military spokeswoman Maj. Avital Leibovich said, "Any Hamas target is a target."

British Prime Minister Gordon Brown, the Vatican, the U.N. and special Mideast envoy Tony Blair all called for an immediate restoration of calm, and the Arab League scheduled an emergency meeting Sunday to discuss the situation.

White House spokesman Gordon Johndroe said, "Hamas' continued rocket attacks into Israel must cease if the violence is to stop. The United States urges Israel to avoid civilian casualties as it targets Hamas in Gaza."

In Gaza City's main security compound, bodies of more than a dozen uniformed Hamas police lay on the ground. One survivor raised his index finger in a show of Muslim faith, uttering a prayer. The Gaza police chief was among those killed. One man, his face bloodied, sat dazed on the ground as a fire raged nearby.

By early evening, 205 Gazans were known to be dead and 388 wounded, Gaza health official Dr. Moaiya Hassanain said. He did not provide figures on civilian deaths. Some of the dead, rolled in blankets, were laid out on the floor of Gaza's main hospital for identification.

Earlier in the day, when the death toll stood at 155, police spokesman Ehud Ghussein had said about 140 Hamas security forces were killed.

Israeli military officials said more than 100 tons of bombs were dropped on Gaza by mid-afternoon. They spoke on condition of anonymity under military guidelines.

Defiant Hamas leaders threatened revenge. Hamas "will continue the resistance until the last drop of blood," vowed spokesman Fawzi Barhoum.

Israel told its civilians near Gaza to take cover as militants began retaliating with rockets, and in the West Bank, moderate Palestinian President Mahmoud Abbas called for restraint. Egypt summoned the Israeli ambassador to express condemnation and opened its border with Gaza to allow ambulances to drive out some of the wounded.

Israeli leaders approved military action against Gaza earlier in the week.

Past limited ground incursions and air strikes have not halted rocket barrages from Gaza. But with 200 mortars and rockets raining down on Israel since the truce expired a week ago, and 3,000 since the beginning of the year, according to the military's count, pressure had been mounting in Israel for the military to crush the gunmen.

Gaza militants fired 30 rockets and mortars Saturday after the air offensive began. A missile hit the town of Netivot, killing an Israeli man and wounding four people, rescue services said.

Dozens of stunned residents, some of them weeping, gathered around the house that took the deadly rocket hit. A hole gaped in one of the walls, which was pocked with shrapnel marks. The crowd broke up after an alert siren went off and everyone went running.

In the town of Kiryat Gat, about 12 miles (20 kilometers) from Gaza, a rocket alert went off for the first time, sending residents into a fluster.

"This is the first time we have ever heard a siren here. I went into a panic," said 20-year-old Lital Cohen. "Soon people won't even leave their homes at all. I still can't fathom it."

Early reports that the town was hit by a rocket for the first time were incorrect.

Streets were nearly empty in Sderot, the Israeli border town that has been pummeled hardest by rockets. A few cars carried panicked residents leaving town. Dozens of people congregated on a hilltop to watch the Israeli aerial attacks.

Israel declared a state of emergency in Israeli communities within a 12-mile (20-kilometer) range of Gaza, putting the area on a war footing.

Protests against the campaign erupted in Arab Israeli villages, the Abbas-ruled West Bank and across the Arab world.

The most violent West Bank response came in the city of Hebron, where dozens of youths, many of them masked, hurled rocks for hours at Israeli forces, who lobbed tear gas and stun grenades in response.

Officials in Bethlehem, Jesus' traditional birthplace, turned off Christmas lights and traders shuttered shops to protest the Israeli attack.

In Amman, several hundred Jordanians protested outside a U.N. complex in the capital Amman. "Hamas, go ahead. You are the cannon, we are the bullets," they cried, some waving the signature green Hamas banners.

In Ein Hilweh, a Palestinian refugee camp in Lebanon, dozens of youths hit the streets and set fire to tires. In Syria's al-Yarmouk camp, outside Damascus, dozens of Palestinian protesters vowed to continue fighting Israel.

The first round of air strikes on Gaza came just before noon.

Hospitals crowded with people, civilians rushing in wounded people in cars, vans and ambulances. "There are heads without bodies .... There's blood in the corridors. People are weeping, women are crying, doctors are shouting, " said nurse Ahmed Abdel Salaam from Shifa Hospital, Gaza's main treatment center.

In the West Bank, Hamas' rival, Abbas, said in a statement that he "condemns this aggression" and called for restraint, according to an aide, Nabil Abu Rdeneh. Abbas, who has ruled only the West Bank since the Islamic Hamas seized power in Gaza in June 2007, was in contact with Arab leaders, and his West Bank Cabinet convened an emergency session.

Israel has targeted Gaza in the past, but the number of simultaneous attacks was unprecedented.

Israel left Gaza in 2005 after a 38-year occupation, but the withdrawal did not lead to better relations with Palestinians in the territory as Israeli officials had hoped.

Instead, the evacuation was followed by a sharp rise in militant attacks on Israeli border communities that on several occasions provoked harsh Israeli military reprisals.

The last, in late February and early March, spurred both sides to agree to a truce that was to have lasted six months but began unraveling in early November.

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AP correspondent Aron Heller reported from Netivot, Israel.