A Palestinian woman reacts next to a wounded man at Nasser hospital following Israeli strikes in Gaza on Saturday. Reuters

Israel pressed its offensive against Hamas in Gaza on Saturday after the United States blocked an extraordinary UN bid to call for a ceasefire in the two-month war.

Hamas and the Palestinian Authority swiftly condemned the US veto as the Hamas-run health ministry put the latest death toll in Gaza at 17,487 people, mostly women and children.

An Israeli strike on the southern city of Khan Yunis killed six people, while five others died in a separate attack in Rafah, the ministry said on Saturday.

Vast areas of Gaza have been reduced to rubble and the UN says about 80 per cent of the population has been displaced, with dire shortages of food, fuel, water and medicine reported.

"It's so cold, and the tent is so small. All I have are the clothes I wear, I still don't know what the next step will be," said Mahmud Abu Rayan, displaced from Beit Lahia in the north.

Wounded Palestinians stand at Nasser hospital following Israeli strikes in Gaza on Saturday. Reuters

A UN Security Council resolution that would have called for an immediate ceasefire was vetoed by the United States on Friday.

US envoy Robert Wood said the resolution was "divorced from reality" and "would have not moved the needle forward on the ground".

Hamas slammed on Saturday the US rejection of the ceasefire bid as "a direct participation of the occupation in killing our people and committing more massacres and ethnic cleansing".

Palestinian Prime Minister Mohammed Shtayyeh said it was "a disgrace and another blank cheque given to the occupying state to massacre, destroy and displace".

The veto was swiftly condemned by humanitarian groups, with Doctors Without Borders (MSF) saying the Security Council was "complicit in the ongoing slaughter".

A wounded Palestinian child sits on the floor at Nasser hospital following Israeli strikes in Gaza on Saturday. Reuters

Israel's military said on Friday it had struck 450 targets in Gaza over 24 hours, showing footage of strikes from naval vessels in the Mediterranean.

The Hamas health ministry reported 40 dead near Gaza City in the north, and dozens more in Jabalia and the main southern city of Khan Yunis.

Agence France-Presse