An injured Palestinian is helped from the rubble following an Israeli missile strike in Rafah, southern Gaza Strip, Saturday, Dec. 27, 2008. Israeli warplanes retaliating for rocket fire from Gaza pounded dozens of security compounds across the Hamas-ruled territory in unprecedented waves of air strikes Saturday, killing at least 155 and wounding more than 310 in the bloodiest day in Gaza in decades.

Gaza City Gaza Strip ? Israeli warplanes rained more than 100 tons of bombs on security sites in Hamas-ruled Gaza Saturday and early today, killing at least 230 people in one of the Mideast conflict’s bloodiest assaults in decades. The government said the open-ended campaign was aimed at stopping rocket attacks that have traumatized southern Israel.

Most of the casualties were security forces, but Palestinian officials said at least 15 civilians were among the dead. More than 400 people were also wounded.

The unprecedented assault sparked protests and condemnations throughout the Arab world, and many of Israel’s Western allies urged restraint, though the U.S. blamed Hamas for the fighting.

But there was no end in sight. The first round of strikes began around noon Saturday followed by successive waves of attacks that continued into the early hours today.

Israel warned it might go after Hamas’ leaders, and militants kept pelting Israel with rockets — killing at least one Israeli and wounding six.

Hundreds of Israeli infantry and armored corps troops headed for the Gaza border in preparation for a possible ground invasion, military officials said, speaking on condition of anonymity under army guidelines.

Prime Minister Ehud Olmert said late Saturday that the goal was “to bring about a fundamental improvement in the security situation.” He added, “It could take some time.”

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

The offensive began eight days after a six-month truce between Israel and the militants expired. The Israeli army says Palestinian militants have fired some 300 rockets and mortars at Israeli targets over the past week, and 10 times that number over the past year.

“There is a time for calm and there is a time for fighting, and now is the time for fighting,” said Israeli Defense Minister Ehud Barak, vowing to expand the operation if necessary.