GAZA CITY, Gaza Strip (AP) -- Israeli airstrikes killed three Palestinian civilians and two militants in the Gaza Strip on Monday and Palestinian rocket squads barraged southern Israel in escalating fighting that defied international truce efforts.
A high school student, a father and daughter were among the dead.
The cross-border violence, touched off by Israel's killing of a top Palestinian militant leader on Friday, has been the worst exchange of fire between Israel and the Hamas-ruled territory in months.
The fighting has so far killed 23 Gazans, including 18 militants, seriously wounded two Israelis, and disrupted the lives of 1 million Israelis living within the range of Gaza rockets.
At a news conference in Gaza City on Monday, masked members of Islamic Jihad's military wing demanded Israel cease fire first and stop targeting militants.
"We warn the leaders of the enemy of the consequences of testing our patience. Our patience is limited and shall be turned into fire and destruction upon them," one of the masked men said.
Chief military spokesman Brig. Gen. Yoav Mordechai said Israel would halt its raids if the rocket fire stopped, but added that the Israeli military would continue to take pre-emptive action to foil militant attack plans.
Israel said it launched Friday's initial airstrike to stop a militant group's plan to infiltrate into Israel through Egypt's Sinai peninsula. In the past, similar flare-ups have died out by themselves or with informal cease-fires negotiated by third parties, often Egypt.
In this case too, Egypt has been trying to mediate an end to the clashes, and Hamas has also appealed to other Mideast countries to join the truce attempts. But by Monday afternoon, there was no sign of progress.
On Monday, Israeli aircraft swooped down on Gaza 11 times by midday, striking what the military said were rocket-launching sites and a weapons storage facility. Two militants, a 16-year-old high school student, and a 65-year-old man and his 30-year-old daughter were killed in four separate raids, Gaza health official Adham Abu Salmia said.
One of the militants was killed while riding a motorcycle. The teenager died while walking to school, and the father and daughter were killed when a missile struck right outside their home, witnesses said.
The Israeli military said the air attacks were in response to continued rocket fire. Police spokesman Micky Rosenfeld said more than two dozen rockets had struck southern Israel by early Monday afternoon. One damaged a preschool building on a communal farm shortly before children were scheduled to arrive, but no one was hurt, Rosenfeld said.
Schools in the area were closed for a second day to avoid casualties, keeping tens of thousands of children from their studies. A day earlier, a rocket struck the courtyard of one of the empty schools.
Also Monday, militants fired three mortar shells into Kerem Shalom, the sole cargo crossing between Israel and Gaza through which 70 percent of all goods that enter the Palestinian territory pass. Two vehicles were hit on the Palestinian side of the crossing, but no one was injured, Israeli officials said. Operations were briefly halted.
Israel says the newly introduced Iron Dome missile defense system intercepted dozens of the more than 190 rockets fired since the clashes erupted over the weekend, and military officials speculated this averted more casualties and damage.
"The vast majority of the rockets shot at Israeli cities were intercepted," said Brig. Gen. Doron Gavish, commander of the defense unit that includes Iron Dome. "This is a new era in military history, there is an effective defense against rockets."
Although military officials are quick to note that Iron Dome will not offer hermetic protection, its success rate raised hopes the military has found a way to rob militants of their most potent weapon -- primitive, short-range rockets that have made life miserable for hundreds of thousands of Israelis by eluding their high-tech military for years.
Israeli Foreign Minister Avigdor Lieberman warned Monday that the continued fire from Gaza "buries any chance of a territorial link between Gaza and the West Bank." The Palestinians want both areas, which lie on opposite sides of Israel, for a future state, along with Israeli-occupied east Jerusalem.
Gaza and the West Bank are today ruled by dueling governments. Hamas is internationally shunned because of its refusal to renounce violence against Israel, and Israel's peace talks with the West Bank government of Palestinian President Mahmoud Abbas stalled years ago.
Although the current fighting shows no signs of subsiding soon, both Hamas and Israel seem eager to avoid the kind of all-out war they waged three years ago.
As it has done since that conflict, Hamas has stayed out of the current clashes for fear of provoking a harsh Israeli retaliation. But that has not stopped other, smaller Gaza factions from attacking Israel, and Israel continues to hold Hamas ultimately responsible for any violence emanating from Gaza.