UN secretary-general Antonio Guterres told the UN Security that hostilities in Israel and Gaza were "utterly appalling", calling for an immediate end to fighting.
Opening the 15-member council's first public meeting on the conflict, Guterres said the United Nations is "actively engaging all sides toward an immediate ceasefire" and called on them "to allow mediation efforts to intensify and succeed".
The death toll in Gaza jumped to 181 overnight, including 47 children, amid an intensive Israeli air and artillery barrage since the fighting erupted last Monday.
Ten people have been killed in Israel, including two children, in thousands of rocket attacks by Hamas and other militant groups.
The UN Security Council met privately twice last week over the worsening violence, but has so far been unable to agree on a public statement because the United States - a strong ally of Israel - did not believe it would be helpful, diplomats said.
"The United Nations is working tirelessly with all sides to restore calm," UN Middle East envoy Tor Wennesland told the council.
"The international community has a crucial role to play. It must take action now to enable the parties to step back from the brink."
Truce efforts by Egypt, Qatar and the United Nations have so far offered no sign of progress.
The US sent an envoy to the region and US president Joe Biden spoke with Israeli prime minister Benjamin Netanyahu and Palestinian president Mahmoud Abbas on Saturday.
