Israeli Prime Minister Benjamin Netanyahu has fiercely defended his country's military campaigns in Iran, Gaza and elsewhere in the Middle East in a speech to the UN General Assembly.

After dozens of delegates walked out in protest as he took to the stage, Netanyahu vowed to continue fighting: "We're going to win. We have no other choice."

In response to the walkout, he said: "If there are any other moral cowards who haven't left the hall, please do so now."

The Israeli leader also rejected accusations that Israel is committing genocide in Gaza.

Hours earlier, in a recorded message Palestinian President Mahmoud Abbas told the UN that Israeli policies - in particular the illegal expansion of Jewish settlements in the occupied West Bank - threatened "the very life and existence of the Palestinian people on their homeland".

He also said it jeopardised the two-state solution, which is an internationally backed formula for peace between Israel and the Palestinians.

Abbas said that Palestinians were being subjected to "killing, destruction, starvation and attempts at displacement, as well as a genocidal war" in Gaza by the Israeli military.

The Palestinian leader was addressing the annual gathering via a video link because he had been denied a US entry visa.