Hamas chief Ismail Haniyeh on Saturday accused Israel of committing war crimes and preventing humanitarian aid from entering the Gaza Strip, as Israel pounds the blockaded territory with air strikes.

"Israeli atrocities amount to war crimes," he said in a letter addressed to United Nations Secretary-General Antonio Guterres that was posted on the Palestinian group's website.

Haniyeh also condemned the "barbaric Israeli siege imposed" on the Palestinian territory, charging that "the Israeli occupation is banning entry of humanitarian aid and medical supplies to the Gaza Strip".

He urged Guterres to pressure Israel into letting humanitarian aid enter into Gaza.

Gunmen from the Islamist Hamas burst across the Gaza border with Israel on 7 October and shot dead more than 1,300 people, including civilians.

In response, Israel has mounted a withering campaign of air and artillery strikes on Gaza that has killed more than 2,200 people, including over 700 children.

Israel has also imposed a "complete siege" on the enclave, halting electricity, water and fuel supplies.

It says supplies will not be resumed until Hamas releases all of the estimated 150 captives its gunmen seized during the cross-border attack.

Around 2.4 million Palestinians live in the Gaza Strip, which has been under a crippling Israeli blockade since Hamas seized power in the coastal enclave in 2007.