Hamas and Israel have created a "hell on Earth" for children in Gaza, UN Secretary General Antonio Guterres said on Thursday before a ceasefire brought 11 days of conflict to an end.
Speaking at the UN General Assembly before Israel's security cabinet approved the truce, Mr Guterres berated the Israeli military and Palestinian militant groups for the carnage.
"I am deeply shocked by the continued air and artillery bombardment by the Israeli Defence Forces in Gaza," he said.
"Indiscriminate firing of rockets by Hamas and other militant groups towards population centres in Israel is also unacceptable ... If there is a hell on Earth, it is the lives of children in Gaza."
On Wednesday evening after the ceasefire began, Mr Guterres told reporters he welcomed the development but pointed to a difficult road ahead for Gaza and stressed the need to restart the peace process with the goal of finding a two-state solution.
"Israeli and Palestinian leaders have a responsibility beyond the restoration of calm to start a serious dialogue to address the root causes of the conflict," he said.
"Gaza is an integral part of the future Palestinian state and no effort should be spared to bring about real national reconciliation that ends the division."
The ceasefire, which began at 2am in Israel, came after the Palestinian foreign minister and Israel's ambassador had accused each other of "genocide" at a special UN meeting on the crisis.
"The whole world stays silent and turns a blind eye to the genocide of whole Palestinian families," Palestinian Foreign Minister Riad Al Maliki said.
Gilan Erdan, the Israeli ambassador to the US and UN, walked out during Mr Al Maliki's speech.
He then alleged there was indifference to "Hamas's charter, which, like the Nazis, is committed to the genocide of the Jewish people".
"We see an attempt to create a false moral equivalence," Mr Erdan said. "Israel makes every effort to avoid civilian casualties. Hamas makes every effort to increase civilian casualties."
The General Assembly meeting had been requested by Niger and Algeria, the current chairs of the Organisation of Islamic Co-operation and the Arab Group at the UN, respectively.
Eleven days of air strikes and rocket attacks killed at least 232 Palestinians in Gaza and 10 people in Israel.
Israel struck Gaza hard on Thursday before the ceasefire agreement.
The Israeli military said it had hit at least three homes of Hamas commanders in Khan Younis, with bombing raids on Deir Al Balah and Gaza city.
Meanwhile, Mr Netanyahu said Iran had launched a drone towards Israel, a claim the military has yet to confirm.
“While we were engaged in these hostilities a few days ago, Iran sent an armed drone from Iraq or from Syria,” he said.