Sunday was the deadliest day since the current fighting between Israel and Gaza began - with 42 Palestinians killed in air strikes.
The Israeli military launched a series of heavy strikes on Gaza City as the country’s prime minister suggested the war against Hamas would continue.
Palestinian militants fired more the than 3,000 rockets at Israel over the past week, the Israeli army claimed.
United Nations Secretary-General António Guterres pleaded for an end to the “utterly appalling” violence and warned that further fighting could plunge the region into “uncontainable crisis".
Early on Monday, explosions rocked the city for 10 minutes in an attack that was heavier, on a wider area and lasted longer than a series of air raids 24 hours earlier.
Israel’s attacks continuing at ‘full force’
In a televised address, Israel's prime minister Benjamin Netanyahu said the country’s attacks were continuing at "full-force" and would "take time".
Israel "wants to levy a heavy price" on the Hamas militant group, he said.
Hamas also pressed on, launching rockets from Gaza towards Israel.
One hit a synagogue in the southern city of Ashkelon hours before evening services for the Jewish holiday of Shavuot, Israeli emergency services said, with no injuries reported.
‘Not seen this level of destruction before’
The hostilities have repeatedly escalated over the past week, marking the worst fighting in the territory that is home to two million Palestinians since Israel and Hamas's devastating 2014 war.
"I have not seen this level of destruction through my 14 years of work," said Samir al-Khatib, an emergency rescue official in Gaza.
"Not even in the 2014 war."
Israel's airstrikes have levelled a number of Gaza City's tallest buildings, which Israel alleges contained Hamas military infrastructure.
Building housing media outlets bombed
Among them was the building housing The Associated Press Gaza office and those of other media outlets.
Sally Buzbee, the AP's executive editor, called for an independent investigation into the airstrike that destroyed the AP office on Saturday.
Mr Netanyahu alleged that Hamas military intelligence was operating inside the building and said on Sunday any evidence would be shared through intelligence channels.
Neither the White House nor the State Department would say if any had been seen.
"It's a perfectly legitimate target," Mr Netanyahu told CBS's Face the Nation.
Asked if he had provided any evidence of Hamas's presence in the building in a call on Saturday with US President Joe Biden, Mr Netanyahu said: "We pass it through our intelligence people."
Mrs Buzbee called for any such evidence to be laid out.
"We are in a conflict situation," she said. "We do not take sides in that conflict. We heard Israelis say they have evidence; we don't know what that evidence is."
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