GAZA CITY, Gaza Strip — Israeli warplanes rained more than 100 tons of bombs on security installations in Hamas-ruled Gaza on Saturday, killing at least 230 people in one of the bloodiest days in decades of the Mideast conflict. The government said the open-ended campaign was aimed at stopping rocket and mortar attacks that have traumatized southern Israel.
More than 400 people were also wounded. Most of the casualties were security forces, but Palestinian officials said at least 15 civilians were among the dead.
A military operation against Hamas had been forecast and demanded by Israeli officials for weeks, ever since a rocky cease-fire between Israel and Hamas broke down completely in early November and rocket attacks began in large numbers against Israel. The Israeli army says militants have fired about 300 rockets and mortar shells at Israeli targets over the past week.
Still, there was a shocking quality to Saturday's attacks, in broad daylight on about 100 sites in the Gaza Strip, as police cadets were graduating, women were shopping at the outdoor market, and children were emerging from school.
The unprecedented assault sparked protests and condemnations throughout the Arab world, and many of Israel's Western allies urged restraint.
The United States blamed Hamas for breaking the cease-fire and attacking Israel.
"These people are nothing but thugs, so Israel is going to defend its people against terrorists like Hamas that indiscriminately kill their own people," said Gordon Johndroe, a spokesman for the National Security Council. "They need to stop. We have said in the past that they have a choice to make. You can't have one foot in politics and one foot in terror."
But there was no end in sight. 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.
Late Saturday, Gaza health official Dr. Moaiya Hassanain said 230 Palestinians were killed and more than 400 were wounded.
Israeli Prime Minister Ehud Olmert said the goal was "to bring about a fundamental improvement in the security situation of the residents of the southern part of the country."
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.
Militants often operate against Israel from civilian areas. Late Saturday, thousands of Gazans received Arabic-language cell phone messages from the Israeli military, urging them to leave homes where militants might have stashed weapons.
Military officials said aircraft released more than 100 tons of bombs in the first nine hours of fighting, focusing initially on militant training camps, rocket-manufacturing facilities and weapons warehouses that had been identified in advance.
A second wave was directed at squads who fired about 180 rockets and mortars at Israeli border communities. Palestinians said Israeli bombs destroyed a mosque early today. The military called it a "base for terrorist activities."
Another target today was the Al Aqsa TV station used by Hamas. Its studio building was destroyed, but the station remained on the air with a mobile unit.
Palestinians counted about 20 airstrikes early today.
"There is a time for calm and there is a time for fighting, and now is the time for fighting," Israeli Defense Minister Ehud Barak said Saturday, vowing to expand the operation if necessary.
Gaza's political leaders, who have been targeted in the past, went into hiding last week. In a speech broadcast on local Gaza television, Hamas' prime minister, Ismail Haniyeh, declared his movement would not be cowed.
Information from the Associated Press and the New York Times was used in this report.