Ten members of a single extended family were killed in an Israeli air strike early Saturday on the western Gaza Strip, medics in the Palestinian enclave said.
The eight children and two women were killed when a three-storey building in Shati refugee camp collapsed following an Israeli strike, medical sources said.
Israeli warplanes struck multiple targets in Gaza overnight, while Palestinian militants fired some 200 rockets at southern Israel, around 30 of which fell short, hitting the ground inside Gaza, the Israeli military said.
Speaking outside Shifa hospital in Gaza City, the father of four of the children, Muhammad al-Hadidi, said he wanted "the unjust world to see these crimes".
"They were safe in their homes, they did not carry weapons, they did not fire rockets," he said of his children, who were killed "wearing their clothes for Eid al-Fitr", the holiday marking the end of Ramadan.
Both Hadidi and Mohammad Abu Hattab, his brother-in-law and host, were away from Hattab's home when it collapsed. The Abu Hattabs' five-month-old baby also survived, AFP reported.
A spokesman for Gaza's Islamist rulers, Hamas, declared the deadly air strike "a war crime in its own right."
The overall death toll in Gaza since Monday now stands at 139, 39 of them children. Around 950 people have been wounded.
On Monday, Hamas fired rockets towards Jerusalem in response to a bloody Israeli police action at the flashpoint Al-Aqsa mosque compound in annexed east Jerusalem, prompting Israel to begin air strikes.
More than 2,300 rockets have been fired at Israel since then, killing nine people, including a child and a soldier. More than 560 people have been wounded.