More than 30 members of two Palestinian families have been killed by Israeli strikes.
The overnight strikes in southern Gaza came as the Palestinian death toll from the two-week conflict passed 500.
Meanwhile, Hamas launched fresh rocket attacks and used tunnels out of Gaza to infiltrate Israel near a town, where 10 militants were killed.
Twenty Israelis, 18 of them soldiers, have died in the conflict.
In Egypt, US Secretary of State John Kerry is due to hold talks aimed at securing a ceasefire.
The UN Security Council has issued a call for an immediate cessation of hostilities, but did not endorse a strongly worded draft resolution backed by Arab states.
UN Secretary General Ban Ki-moon has criticised an Israeli operation in the densely populated area of Shejaiya on Sunday as an atrocious action.
At least 67 people were reported killed in the assault on Shejaiya, which Israel said was a terror stronghold.
