Smoke rises in Gaza City after an Israeli airstrike on Saturday.
Updated at 4:55 p.m. ET.
The end of the latest cease-fire in the Gaza Strip has been marked by intense Israeli airstrikes against Hamas targets.
The U.S. and United Nations have condemned the resumption of hostilities that comes at the end of a three-day truce on Friday.
NPR's Alice Fordham, reporting from Gaza, says "The barrage came after Palestinian officials expressed frustration with peace talks in Cairo. They want more freedom of movement and goods into and out of the Gaza strip, among other demands. But Israel, which controls most crossings, has not yet budged on the issue, and since rocket fire re-started has suspended its engagement in the talks."
Reuters reports that Palestinian representatives at the Cairo talks have said they will leave on Sunday if Israel does not agree to resume unconditional negotiations.
In Jerusalem, NPR's Jackie Northam says airstrikes hit 20 targets overnight, killing five Palestinians. The BBC says a total of 33 sites were hit early Saturday. Israel says Hamas has fired more than 70 rockets into southern Israel since the truce expired.
The Associated Press quotes a Palestinian health official as saying three bodies were found under the ruins of a mosque, including that of a senior Hamas official.
U.N. spokesman Chris Gunness says 65,000 homes have already been destroyed in the fighting.
Northam says that an Israeli delegation conducting talks aimed at ending the fighting, which has claimed more than 1,900 Palestinians and dozens of Israelis, has left Egypt and it is not clear if or when it will return to Cairo.
"The talks are private — but there are reports from Palestinian officials that Israel refused to grant key demands by Hamas, such as fully lifting a 7-year blockade of the Gaza Strip by Egypt and Israel. A Palestinian delegation remains in Cairo. Egypt's foreign ministry said there had been progress made in the negotiations," she says.