The death toll in Gaza passed 400 on Sunday as Israel pressed its biggest offensive in the enclave in five years, Palestinian health officials said.
"410 people have been killed since the war started and more than 3,020 people have been injured, most of them civilians," deputy health minister Yussef Abu Rish told reporters at Shifa hospital in Gaza City.
The vast majority of Sunday's dead were in the Shejaiya neighbourhood between Gaza City and the Israeli border, where more than 50 people were killed in a blistering bombardment which began overnight, medics said.
Following an urgent appeal from the International Committee of the Red Cross, both sides agreed to halt fire in the neighbourhood, with a two-hour humanitarian lull going into force at 1030 GMT.
As the ceasefire got under way, a convoy of ambulances entered Shejaiya, with medics seen picking up at least three dead bodies, including that of a man with his intestines hanging out and his head completely destroyed, an AFP correspondent reported.
But shortly afterwards, the sound of small arms fire was heard in the area.
The Israeli army said Hamas had "not stopped shooting" and that it was responding accordingly.