Strikes flew across the Gaza border in rapid succession Thursday, as Israel responded to an onslaught of militant rocket attacks by targeting "terror sites."
The sudden increase in violence has raised fears of a widening conflict that could lead to an Israeli ground assault.
At least 245 rockets from Gaza have been fired into Israel since "Operation Pillar of Defense" began Wednesday, the Israeli military said. Israel's Iron Dome defense system has intercepted more than 80, the Israel Defense Forces said. And Israel has responded by targeting 156 "terror sites," the IDF said.
Sources with Hamas, which controls the government in Gaza, and Palestinian Islamic Jihad gave similar figures, saying more than 140 strikes have hit Gaza and that more than 160 rockets and shells have been fired into Israel.
At least three Israelis were killed and four were wounded when a rocket struck an apartment building in the town of Kiryat Malakhi on Thursday, an Israeli police spokesman said. "Good morning to our friends in America," the IDF tweeted. "While you were sleeping, 3 Israelis were killed when a rocket hit their house."
Thirteen people, including two children, were reportedly killed in airstrikes in Gaza on Thursday, said Dr. Asraf el-Qdra of Medical Aid for Palestinians. Of the casualties, nine were Hamas militants, he said. But Hamas spokesman Osama Hamdan told CNN that the 13 dead included five children. He identified only two as Hamas militants. Hamdan also insisted that Israel "started the war."
"We are defending ourselves," he said, arguing that Israeli Prime Minister Benjamin Netanyahu was looking to cement support in advance of an election in two months.
People have been wounded on both sides as well
Palestinian officials said more than 120 people have been wounded since the Israeli strikes began this week in Gaza. Israel has reported several people wounded, and another three soldiers injured Thursday morning by rockets from Gaza.
Palestinian President Mahmoud Abbas, who leads the Palestinian Fatah movement based in the West Bank, is cutting short a visit to Europe to follow developments of "the Israeli aggression on the Gaza strip," PLO Executive Committee member Saeb Erakat said.
The violence comes after months of rocket attacks on southern Israel by Palestinian militants, Israel said.
British Foreign Secretary William Hague issued a statement saying he is "gravely concerned" and calling on all sides to avoid civilian casualties.
"Hamas bears principal responsibility for the current crisis. I utterly condemn rocket attacks from Gaza into southern Israel by Hamas and other armed groups. This creates an intolerable situation for Israeli civilians in southern Israel, who have the right to live without fear of attack from Gaza. The rocket attacks also risk worsening the plight of Palestinian civilians in Gaza, which is already precarious."
Hague called on "those in the region with influence over Hamas to use that influence to bring about an end to the attacks. I also strongly urge Israel to do their utmost to reduce tension, avoid civilian casualties and increase the prospects for both sides to live in peace."
Israel says it has called thousands of residents in Gaza to warn them of strikes and dropped leaflets in Gaza warning Palestinian civilians to "avoid being present in the vicinity of Hamas operatives," the IDF said.
It also uses "roof knocking" -- targeting a building "with a loud but non-lethal bomb that warns civilians that they are in the vicinity of a weapons cache or other target. This method is used to allow all residents to leave the area before the IDF targets the site with live ammunition." And "whenever possible," the IDF said, it "singles out terrorists and targets them in a way that will endanger few or no bystanders."
The U.N. Security Council held an emergency closed-door session late Wednesday about the crisis.
International diplomats hope to stave off a repeat of Israel's widely condemned 2008 assault that saw its forces go into Gaza after a similar spate of rocket attacks by Palestinian militants.
Q&A: Gaza strikes could be beginning of ground attack
"In short, the message that must resonate from this meeting is 'the violence has to stop,' " Hardeep Singh Puri, president of the Security Council for November, told reporters.
Turkish Foreign Minister Ahmet Davutoglu, meanwhile, called the violence a sign of "Israeli aggression," the semiofficial Anadolu Agency reported.
Russian Foreign Ministry spokesman Alexander Lukashevich, on Twitter, said Russia "is concerned about the deteriorating situation in Gaza; the increased use of force is unacceptable." He said Russia urges "all sides to end the military confrontation immediately."
In Washington, Rep. Chris Van Hollen, the top Democrat on the House Budget Committee, said, "Hamas continues to rain rocket attacks into Israel. Israel, of course, has the right to defend itself. Hamas has dedicated itself to the destruction of Israel. They've never