Hamas' exiled leader on Wednesday called off a ceasefire with Israel and militants threatened to attack Americans after 18 members of a family, including eight children, were killed in an Israeli artillery barrage on a densely populated Gaza neighborhood.
It was the highest number of Palestinian civilians killed in a single strike since fighting erupted six years ago, and undermined Palestinian President Mahmoud Abbas' attempts to form a more moderate government and renew a peace process with Israel.
Abbas condemned the "terrible, despicable crime," and the international community criticized the deaths. Israel, promising a swift inquiry, expressed regret for harming civilians.
The shelling occurred early on Wednesday as residents were sleeping in the northern Gaza town of Beit Hanoun, the focus of a weeklong military offensive aimed at stopping rocket fire. Israeli troops had pulled out of the town just 24 hours earlier, and the rocket attacks resumed almost immediately.
The Israeli shells landed around a compound of four apartment buildings on a small side street. The explosions left holes in the buildings, owned by four brothers from the al-Athamna family, and sent panicked residents scurrying outside. Additional salvos landed, hitting the people and flooding a dusty alleyway in a pool of blood.
"Shells were fired directly onto the people who were rushing out of the house," said Akram al-Athamna, a relative of the victims. "There was blood everywhere."
Another family member, 14-year-old Asma al-Athamna, said she saw her mother, older sister and brother-in-law die as they fled their home.
"I was behind them and I was wounded," the weeping girl said from her hospital bed. Her two-year-old niece, Malak, lay in an adjacent bed, recovering from shrapnel wounds to her face.
The family is prominent in Beit Hanoun and includes several doctors and professionals. Family members said they had fled during the Israeli offensive, returning home after Tuesday's pullout.
Bits of dismembered bodies were plastered to walls of the damaged buildings and lying on the ground. A woman's head scarf, children's boots and slippers, and a pair of jeans -- all burnt -- were strewn outside.
Weeping relatives gathered outside the homes. One man dipped his hand in victims' blood and smeared it over his face.
"God avenge us, God avenge us," he wailed.
A young man, standing in the bloodied alleyway, said an infant girl had been blown to pieces.
"I tried to look for her head, I tried to look for her head," he shrieked, then sank to the ground, weeping.
Health workers said some 60 people were wounded, including 26 children.
In Damascus, Syria, Khaled Mashaal, the exiled leader of Hamas, said the group would no longer honor a February 2005 truce and called for renewed attacks on Israel. He urged other militant groups to join the struggle.
"The armed struggle is free to resume, and the resistance is dictated by local circumstances," he told a news conference. "There must be a roaring reaction so that we avenge all those victims." Other major militant groups pledged to follow suit.
The declarations raised the prospect of a new wave of suicide bombings and large-scale fighting with Israel. Although violence has persisted since the truce declaration, including the kidnapping of an Israeli soldier by Hamas-linked militants in June, there has been a sharp drop in fighting. Hamas has not carried out a suicide bombing since August 2004, after killing scores of Israelis in such attacks over the previous four years.