At least 100 Palestinians and 13 soldiers have been killed as Israel ramped up a major military offensive in the bloodiest single day in Gaza in five years.
The Palestinian president called for an immediate meeting of the UN Security Council as regional leaders met in Doha for urgent talks on a ceasefire.
As the Palestinian death toll soared to 438, a spokesman for the Gaza emergency services said more than a third of the victims were women and children.
The Israeli army said 13 soldiers had been killed inside Gaza on the third day of a major ground operation.
"Over the course of the day, 13 soldiers from the IDF's Golani Brigade were killed in combat in the Gaza Strip," a statement said.
Their deaths raised to 18 the number of soldiers killed since the ground operation began late on Thursday.
It was the largest number of soldiers killed in combat since the 2006 Lebanon war.
More than half of Sunday's Palestinian victims were killed in a blistering hours-long Israeli assault on Shejaiya, near Gaza City, which began before dawn and has so far claimed 62 Palestinian lives, with another 250 wounded.
With ambulances unable to reach the area, the International Committee of the Red Cross called for an urgent temporary ceasefire to allow paramedics to evacuate the dead and wounded, which was agreed on by the two sides.
Inside Shejaiya, there were hellish scenes of carnage and chaos as a convoy of ambulances moved in, an AFP correspondent said.
Entire buildings were collapsed on themselves or strewn into the streets, while others were ablaze, sending pillars of dark smoke skywards.
There were also bodies, blackened and charred almost beyond recognition, some with whole limbs missing.
As the violence raged, Palestinian president Mahmud Abbas arrived in Qatar to discuss a ceasefire with Hamas leader Khaled Meshaal, and UN chief Ban Ki-moon arrived later to push truce efforts.
"I am calling for an urgent session tonight of the UN Security Council," Abbas said in a speech broadcast on Palestinian TV.
"What the occupation forces did today in Shejaiya is a crime against humanity," he said.
"Those who committed it will not go unpunished."
Ban also condemned the "atrocious action" in Shejaiya and urged Israel to "exercise maximum restraint".
"Too many innocent people are dying...(and) living in constant fear," he told a news conference in Doha.
So far, truce efforts have been rejected by Hamas which has pressed on with its own attacks, undaunted by the Israeli bombardment by land, sea and air.
UNRWA has opened 61 of its schools to shelter those fleeing, with more than 81,000 people taking refuge in them, the refugee agency said.
