Israel has said rocket fire from Gaza has "made continuation of talks impossible," trading blame with Palestinian negotiators over the collapse of the ceasefire.
Spokesman Mark Regev responded to Palestinian negotiator Azzam al-Ahmed's charge that Israel had thwarted the talks that broke down on Tuesday after Israel recalled its negotiators from Egypt, accusing Hamas of violating a truce.
"The Cairo process was built on a total and complete cessation of all hostilities and so when rockets were fired from Gaza, not only was it a clear violation of the ceasefire but it also destroyed the premise upon which the talks were based," Regev said, according to the Reuters news agency.
A week-long truce in Gaza collapsed with both sides blaming each other after Palestinian fighters launched rockets into Israel and Israel attacked "terror sites" inside the enclave.
Al Jazeera's Jane Ferguson said at least six children had been killed in the airstrikes since the truce disintegrated.
"There is now this fallout row, essentially over who started it," our correspondent said. "Whoever broke the truce, it seems the exchange of rocket fire into Israel and airstrikes on Gaza is unlikely to end today."
The Israeli military launched attacks on at least 10 sites in Gaza on Tuesday, killing at least three people, and recalled its team working on a permanent ceasefire with Palestinians in Cairo after three rockets landed in Israel.
Further shelling on Wednesday killed another 21 Palestinians, raising the death toll in Gaza to 2,035.
Hamas, the Palestinian group that runs Gaza, said Israel had targeted Mohammed Deif, the head of its armed wing.
A series of airstrikes on the area of Deif's house resulted in the death of his wife and child.
Hamas said Deif was alive and still in command.
"The occupation will pay for its crimes against Palestinian civilians and those living around the Gaza border will not return home until Mohammed Deif decides," Hamas spokesman Sami Abu Zuhri said in a statement.
An Israeli government official said: "In response to Hamas's violation of the truce, the prime minister and defence minister have ordered the IDF [Israeli army] to once more attack terror sites in the Gaza Strip."
The Qassam Brigades, Hamas's armed wing, said on Twitter that it had fired rockets towards Tel Aviv. No one was injured in the attack on the city, the Israeli army said.
In Cairo, Palestinian negotiators declared the ceasefire talks over, and said they would leave Egypt on Wednesday.
"We told the Egyptians we are ready to return to the talks once they find the proper atmosphere," said Azzam al-Ahmad, the Palestinian negotiator, adding that the Palestinians had submitted a final ceasefire proposal.
"It's clear the Israelis are not interested in the ceasefire. We did not hear from them. We were willing to, but we did not hear from them," he said.
|INTERACTIVE: Gaza Under Attack
Hamas is seeking an end to a seven-year Israeli-Egyptian blockade that has battered Gaza's economy, while Israel wants guarantees that Hamas will disarm.
In nearly a week of indirect talks, Egypt appears to have made little headway in resolving the differences. Late on Monday, it secured a 24-hour extension to a temporary truce to allow more time for a last-ditch attempt to reach a longer-term deal.
An Egyptian compromise proposal calls for easing the blockade, but not lifting it altogether and opening the territory's air and seaports as Hamas has demanded.
While the plan does not require Hamas to give up its weapons, it would give Western-backed President Mahmoud Abbas, whose forces were ousted by Hamas in 2007, a foothold back in Gaza running border crossings and overseeing internationally-backed reconstruction.