Israeli air strikes killed at least 181 Palestinians, including 47 children, amid an intensive air and artillery barrage since the fighting erupted last Monday.
Ten people have been killed in Israel, including two children.
With no sign of an end to the worst outbreak of Israeli-Palestinian violence in years the United Nations Security Council was due to meet later on Sunday to discuss the hostilities, reports Reuters.
At least 33 Palestinians, including eight children, were killed in air strikes on Sunday.
The pre-dawn attacks were on houses in the centre of Gaza City, Palestinian health officials said. A spokesman for the Israeli military said he would look into these reports.
Palestinians working to clear rubble from a building wrecked in the air strikes recovered the bodies of a woman and man.
"These are moments of horror that no one can describe. Like an earthquake hit the area," said Mahmoud Hmaid, a father of seven who was helping with the rescue efforts.
Across the border in the Israeli city of Ashkelon, Zvi Daphna, a physician, whose neighborhood has been struck by several rockets, described a feeling of "fear and horror".
The Israeli military said that Hamas, the Islamist group that runs Gaza, and other armed groups have fired more than 2,800 rockets from the enclave in six days.
This was more than half the number fired during 51 days in a 2014 war between Hamas and Israel, the military said, and more intensive even than Hezbollah's bombardment from Lebanon during the 2006 war between Israel and the Iran-backed Shi'ite group.
Many of the rockets have been intercepted by an Israeli anti-missile system while some have fallen short of the border.