Israeli fire killed at least 43 Palestinians in the Gaza Strip early on Wednesday.
Israeli tank shells and air strikes on houses and a school in Jebalya in northern Gaza killed at least 43 people and wounded many others, including 20 in a UN school.
Reuters reported quoting health ministry spokesman Ashraf Al-Qidra.
Among the dead were a medic and an infant.
The Jewish state said it targeted Islamist militants at dozens of sites across the coastal enclave.
Over Gaza issue, Egyptian mediators prepared a revised ceasefire proposal.
Israel's Channel Two TV said progress was being made to achieve a deal in Cairo, where a Palestinian delegation was expected to arrive for discussions.
An Israeli army spokeswoman said she was checking for details.
Eight people, including five members of the same family in Jebalya, were killed in other strikes, Gaza officials said.
Hospital officials put the total number of Palestinians killed in the conflict at 1,224, most of them civilians.
On the Israeli side, 53 soldiers and three civilians have been killed since the start of the offensive on July 8.
Israel launched its offensive in response to rocket salvoes fired by Gaza's dominant Hamas Islamists and their allies.
UNRWA, the main UN relief agency in Gaza, said it was at "breaking point" with more than 200,000 Palestinians having taken shelter in its schools and buildings following calls by Israel for civilians to evacuate whole neighbourhoods before military operations.
The agency acknowledged that it had found a cache of rockets in one school. but blamed no particular party.
However, a reclusive Hamas military leader rules out a ceasefire with Israel to end Gaza violence, at the end of a destructive day, BBC adds.
