CBS News chief foreign correspondent Lara Logan, in an exclusive report from the scene, reports at least six people were killed by the airstrike and an as yet undetermined number of people were wounded.
The death toll is expected to rise.
Israeli military officials say Mohammed Deif, the Palestinian militant who has topped Israel's wanted list for a decade, is among those wounded in the airstrike.
Hamas denies that Deif was wounded, but confirms that he was a target of the airstrike. In a cell phone text message, the group says "commander Mohammed Deif" and his colleagues have survived.
Hamas official Ismail Radwan pledged to hit back at Israel. "It was a terrible, bloody massacre, and the Zionists will pay a heavy price for it," he said.
Deif - allegedly a master bombmaker - has been targeted several times in Israeli assassination attempts and in the past has been reported to have been seriously wounded. Israel holds him responsible for many suicide bombing attacks in Israel over the past decade.
Palestinians say a high level meeting of Hamas commanders was in progress at the residence in Gaza City just before the airstrike. Nervous Hamas officials carefully inspected the bodies but refused to comment.
After the Israeli attack, hundreds of Palestinians gathered at the flattened house, vowing revenge and calling the Israelis terrorists.
"As bodies were pulled from the rubble here, you could feel the crowd, the anger of the crowd," Logan reports. "As people surged forward, it almost seemed to go out of control and then, in one dramatic moment, a man in the crowd began a chant, a traditional Palestinian chant of resistance, also vowing revenge."
"Hundreds of people," Logan continues, "who in one moment, were surging forward in anger, almost out of control, suddenly stood rooted to the spot and repeated this chant, which has been a chant of resistance against the Israelis for the past few years."
Israel says it launched the airstrike in the Sheik Radwan neighborhood, a Hamas stronghold, because Hamas commanders there were planning more attacks on Israel.
Israel also says the home it attacked was a "meeting place for terrorists." Israeli officials also confirm that Israeli forces are operating in southern Gaza as part of an effort to win the release of a captured soldier.
Hours after the airstrike, rescue workers were still digging through the rubble left from the strike, which destroyed the house.
Abu Obeideh, spokesman for the military wing of Hamas, issued an unusually strong condemnation, using language employed only when Israel has assassinated top Hamas leaders. "We will make the leaders of the Zionist regime regret this Nazi crime," said part of his long statement.
But Hamas officials said they did not know who was killed.
The airstrike is the latest blow by Israel in a two-week offensive in the region with an incursion further south.
There are unconfirmed reports that Israeli troops are conducting house-to-house searches, apparently to look for the soldier.
"We know that he is in Gaza Strip," Brig. Gen. Ido Nehushtan, a senior Israel army official told CBS News.
Asked if he knew anything more specific, he said, "I think that Gaza Strip is not very big portion of land ... We have patience — and we have no other option."
Israel launched its offensive on June 28, three days after Palestinian militants linked to the Hamas-led government captured an Israeli soldier in a cross-border raid. The operation was expanded last week to halt Palestinian militants from firing homemade rockets into Israel.
Prime Minister Ehud Olmert and his defense minister, Amir Peretz, ordered the new incursions into Gaza after Hamas leader Khaled Mashaal said Monday he would not free the captive soldier, 19-year-old Cpl. Gilad Shalit, security officials said on condition of anonymity because of the sensitivity of the operation.
Mashaal called Shalit a prisoner of war and demanded a prisoner swap — which Olmert has ruled out.
Responding to Mashaal's statement, Shalit's father, Noam, called on Hamas to allow the Red Cross to visit his son. Under Geneva Conventions, the Red Cross is supposed to have access to prisoners of war.
Israel has demanded the unconditional release of its soldier to end the offensive.
The invasion — Israel's largest ground operation in Gaza since withdrawing from the area last year — has caused widespread destruction, knocked out much of Gaza's power supply and left more than 50 Palestinians dead, most of them gunmen. One Israeli soldier has died.
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