GAZA CITY, Gaza Strip (AP) -- Israeli airstrikes killed three Palestinians including a schoolboy in the Gaza Strip on Sunday, officials said, while Gaza rocket squads fired salvos into southern Israel, deepening the worst round of violence between the sides in more than a year.
The Israeli military said its aircraft targeted rocket launchers and a Gaza health official said the 12-year-old boy, a 60-year-old farm guard and a militant were killed as the exchanges of fire entered their third day and Egyptian efforts to achieve a cease-fire faltered.
"There is no room to talk about calm considering the continued Zionist aggression against Gaza," Khaled Batch, a leader of the Islamic Jihad militant faction in Gaza, told The Associated Press.
Gaza health official Adham Abu Salmia said the militant was killed at a rocket launching site in Gaza City. The boy was hit while walking with a friend to school in the northern city of Jebaliya and the guard died while walking with his dog, who was also killed, he added.
Israeli police spokesman Micky Rosenfeld said the dozen rockets launched from Gaza on Sunday caused no injuries or damage. The military claims more casualties were averted since the fighting began because Iron Dome missile defense batteries intercepted more than 90 percent of the rockets they targeted.
Israeli airstrikes have killed 16 Gazan militants and two civilians, and militants have fired more than 120 rockets at Israel, seriously wounding a civilian, since the fighting erupted on Friday with an Israeli air assault that killed the commander of a militant group.
Israel accused Zuhair al-Qaissi of plotting an infiltration attack into Israel from Egypt's lawless Sinai peninsula, similar to the one they claim he orchestrated in August, which killed eight Israelis. His militant group, the Hamas-allied Popular Resistance Committees, has never taken responsibility for that raid.
Israeli Prime Minister Benjamin Netanyahu said Israel remains prepared for a strike from the Sinai and pledged to deploy more Iron Dome missile defense batteries in the future.
"We exacted a heavy price and continue to exact it," Netanyahu said of the Israeli strikes on Gaza. "We will continue to overcome these terror threats."
Chief military spokesman Brig. Gen. Yoav Mordechai said the army took into account the possibility that the assassination of al-Qaissi would touch off broader fighting when it launched the attack.
"We will continue to attack the terror cells that try to attack us," he told Israel Radio.
Some 1 million Israelis are within range of rocket fire from Gaza, and on Sunday, schools throughout the area and Ben-Gurion University in Beer Sheva were closed because of the fighting. Rosenfeld said police stepped up their presence in southern Israel.
Israel and Gaza militants have frequently traded low-level fire since the 2009 war, but a flare-up of this intensity is rare. The United Nations and the U.S. State Department have condemned the violence and called on both sides to exercise restraint.
Gaza's militant Islamic Hamas rulers have denounced the Israeli airstrikes but their fighters have not attacked Israel, leaving that to other, smaller Palestinian militant groups.
Hamas has largely avoided direct attacks on Israel since the Jewish state conducted a bruising three-week war against the militant group in early 2009 that killed hundreds of Gazans and destroyed many Hamas facilities. But the Iranian-backed Hamas has been smuggling increasingly sophisticated weapons into the seaside territory and Israel holds it responsible for all violence emanating from Gaza.
Israeli Foreign Minister Avigdor Lieberman told Israel Radio on Sunday that there was no point in Israel's launching another large-scale offensive in Gaza unless it sets out to topple the Hamas regime. Lieberman wouldn't say whether such an operation was planned but noted that the violence from Gaza was "unacceptable and we won't reconcile ourselves to it."
Despite Lieberman's tough talk, neither side is believed to be interested in all-out war.
Egypt, which has helped arrange truces in the past, has been trying to arrange a cease-fire, but an official there said the Egyptians were encountering resistance from two militant groups, al-Qaissi's PRC and Islamic Jihad. Both factions want guarantees that Israel won't target their groups, he said, but that is something Egypt cannot deliver.
The Egyptian official spoke on condition of anonymity because he was not at liberty to divulge details of cease-fire efforts.
Hamas officials also said they have been in touch with leaders in Qatar, Turkey and the Arab League in an effort to contain the violence.
Hanan Ashrawi, a Palestinian spokeswoman and senior Palestine Liberation Organization official, said Palestinian President Mahmoud Abbas had also been touch with leaders in Gaza and Egypt to try to restore calm. Abbas has had little on-the-ground influence in Gaza since Hamas violently overran the territory in June 2007.