UN humanitarian chief Martin Griffiths on Friday said Gaza had become "uninhabitable" after relentless bombing by Israeli forces in retaliation for the Hamas militant group's attack in October.

"Three months since the horrific 7 October attacks, Gaza has become a place of death and despair," Griffiths said in a statement.

"Gaza has simply become uninhabitable. Its people are witnessing daily threats to their very existence - while the world watches on.

"The humanitarian community has been left with the impossible mission of supporting more than two million people."

With much of the Gaza Strip already reduced to rubble, air strikes continued through the night in the southern cities of Khan Yunis and Rafah as well as parts of central Gaza, AFP correspondents reported Friday.

The Israeli army said its forces had "struck over 100 targets" across Gaza over the past 24 hours, including military positions, rocket launch sites and weapons depots.

"We continue to demand an immediate end to the war, not just for the people of Gaza and its threatened neighbours, but for the generations to come who will never forget these 90 days of hell and of assaults on the most basic precepts of humanity," Griffiths said.

"This war should never have started. But it's long past time for it to end."

The Hamas assault on October 7 resulted in the deaths of around 1,140 people in Israel, mostly civilians, according to an AFP tally based on the latest official Israeli figures.

In response, Israel launched a bombardment and ground invasion that have killed at least 22,600 people, most of them women and children, according to the Gaza health ministry.