US ambassador to the UN Linda Thomas-Greenfield speaks to delegates during the UNGA in New York. Reuters

Israel came under pressure Wednesday from its allies over its war in Gaza, with key backer the United States criticising its bombing in response to the October 7 attacks as "indiscriminate".

The United Nations General Assembly also overwhelmingly backed a non-binding resolution demanding an immediate humanitarian ceasefire in the devastated territory.

Vowing to destroy Hamas and to bring the hostages home, Israel launched a withering offensive on Gaza, which is ruled by the group.

Israel faced growing diplomatic isolation in its war against Hamas as the United Nations demanded an immediate humanitarian ceasefire in Gaza and US President Joe Biden told the longtime ally its "indiscriminate" bombing of civilians was hurting international support.

After dire warnings from UN officials about a deepening humanitarian crisis in Gaza, the 193-member UN General Assembly on Tuesday passed a resolution calling for a ceasefire with three-quarters of member states voting in favour.

Delegates of Egypt applaud after looking at the voting results during the meeting of the UNGA in New York. Reuters

"The price of defeating Hamas cannot be the continuous suffering of all Palestinian civilians," the leaders of Canada, Australia and New Zealand said separately in a joint statementcalling for a ceasefire.

The Palestinian Authority welcomed the resolution and urged countries to pressure Israel to comply. A Hamas official in exile, Izzat El-Reshiq, in a statement on Telegram echoed that reaction, saying Israel should "stop its aggression, genocide, and ethnic cleansing against our people."

The US and Israel, which argue a ceasefire only benefits Hamas, voted against the measure along with eight other countries.

According to the Hamas-run health ministry, the war has killed more than 18,400 people, mostly women and children.

The ministry reported Wednesday that at least another 50 people were killed in the latest wave of Israeli air strikes across the territory.

Palestinian child wounded in the Israeli bombardment of the Gaza Strip are brought to a hospital in Rafah. AP  

Biden told a campaign event in Washington that Israel had "most of the world supporting it" after the Hamas attack.

"But they're starting to lose that support by the indiscriminate bombing that takes place," he said.

Speaking later Tuesday at a news conference, Biden toned down his comments.

Reiterating the United States' support for Israel, he said that "the safety of innocent Palestinians is still of great concern".

Washington has been calling for weeks for Israel to take more care to avoid civilian casualties in Gaza, saying that too many Palestinians have been killed.

Agencies