More than 400 people have been killed in all.
At least 100 people- including 87 Palestinians and 13 Israeli soldiers- were killed Sunday, the bloodiest day yet since fighting broke out 13 days ago between Israel and Palestinian militant group, Hamas.
Reports say 67 of the victims were killed in one location.
Israel suffered its worst death toll since the latest conflict began nearly two weeks ago, with 13 of its soldiers among the dead. The deaths brings to 18 the number of Israeli soldiers who have been killed in the offensive.
Palestinian President Mahmoud Abbas said the deaths in the Shejaiya district east of Gaza City were a “massacre”. Witnesses spoke of bodies lying in the streets, according to the BBC.
Fighting has intensified between the two sides despite attempts at a ceasefire.
A humanitarian truce was agreed to allow civilians leave the area, but lasted less than an hour.
The ceasefire in Shejaiya was meant to last for two hours, but reports say fire broke out soon after it was declared.
Gaza’s officials were quoted by Reuters news agency as saying that said at least 405 Palestinians, many of them civilians, have been killed and about 2,600 wounded since Israeli air and naval bombardments began on July 8, followed by a ground push on Thursday.
Fighting has continued despite interventions by Egypt, Qatar, France and the United Nations, among others.
Hamas rejected one Egyptian-brokered truce, saying any deal must include an end to a blockade by Israel and a recommitment to a ceasefire reached after an eight-day war in Gaza in 2012.