Palestinians wait at the Rafah border crossing between the Gaza Strip and Egypt Gaza Strip on Saturday, Oct. 14. AP-Yonhap

Thousands of Palestinians fled the north of the Gaza Strip on Saturday from the path of an expected Israeli ground assault, while Israel pounded the area with more air strikes and said it would keep two roads open to let people escape.

Israel has vowed to annihilate the Hamas militant group that controls Gaza in retaliation for a rampage by fighters, who stormed through Israeli towns a week ago, gunning down civilians and making off with scores of hostages. Some 1,300 were killed in the worst attack on civilians in Israel's history.

Israeli forces have since put the Hamas-run Gaza Strip, home to 2.3 million Palestinians, under a total siege and bombarded it with unprecedented air strikes. Gaza authorities say more than 2,200 people have been killed, a quarter of them children, and nearly 10,000 wounded.

Israel had given the entire population of the northern half of the Gaza Strip, which includes the enclave's biggest settlement Gaza City, until Saturday morning to move south. It announced overnight that it would guarantee the safety of Palestinians fleeing the area on two main roads until 4:00 pm. (1300 GMT).

"Around the Gaza Strip, Israeli reserve soldiers in formation (are) getting ready for the next stage of operations," Israeli military spokesperson Lieutenant Colonel Jonathan Conricus told a video briefing early on Saturday.

"They are all around the Gaza Strip, in the south, in the centre and in the north, and they are preparing themselves for whatever target they get, whatever task."

Hamas has told people not to leave and says the two roads Israel has declared open are unsafe. It says dozens of people have been killed on them in strikes on cars and trucks carrying refugees Friday, which Reuters could not independently verify. Israel says Hamas is preventing people from leaving to use them as human shields, which Hamas denies.

In Gaza City's Tel Al-Hawa neighbourhood, part of the area Israel has ordered evacuated, warplanes bombed a residential area during the night, hitting several houses, according to residents who posted appeals on social media platforms.

Hundreds of residents of the area took refuge at the nearby Quds hospital and planned to join those fleeing to the south in the morning.

"We lived a night of horror. Israel punished us for not wanting to leave our home. Is there brutality worse than this?", a father of three told Reuters by telephone from the hospital, declining to give his name for fear of reprisals.

"I was never going to leave, I prefer to die and not leave, but I can't see my wife children die before my eyes. We are helpless."

In Khan Younis, in the southern Gaza Strip, Israeli planes struck a four-storey building, killing and wounding several people. Neighbours rushed to rescue people trapped in rubble.

"This is a genocide, not a war, it's genocide. And it's an attempt to displace the people of the Gaza Strip, but this will not happen," said neighbour Mohammad Sadeq. "Martyrs are stuck under the rubble and until now neither us nor the medics nor civil defence were able to take them out."

Palestinians wounded in Israeli air strikes on Gaza Strip are brought to al-Aqsa hospital in Deir el-Balah City, Gaza Strip, Saturday, Oct. 14. AP-Yonhap

The attacks on Israel plunged the nation into deep mourning and galvanised the country, which mobilised hundreds of thousands of reservists within days.

Families of the Israeli hostages kidnapped by Hamas are terrified for their safety. Avichai Brodetz, a farmer from Kibbutz Kfar Aza whose wife and three children were taken captive to Gaza, set up a camp outside the Israeli army headquarters to focus attention on their plight.

"The first thing that needs to happen is the release of the women and children," he told reporters. "I don't want to be political, I don't want to stand here with you. I love my friends and my home and my kibbutz. I hope we can return there and you'll never see me again."

Israel's attacks on Gaza have not halted Hamas missile strikes deep into Israeli cities. Air raid sirens wailed in central Israel on Saturday morning and rockets smashed into a greenhouse in Ashkelon and wounded four people at a kibbutz.

The only route out of Gaza that is not under Israeli control is a checkpoint with Egypt at Rafah. Egypt officially says its side is open, but traffic has been halted for days because of Israeli strikes on the Palestinian side.

Egyptian security sources said the Egyptian side is being reinforced and Cairo has no intention of accepting a mass influx of Palestinian refugees.

A senior U.S. State Department official said the United States was working with Egyptian, Israeli and Qatari officials to open the crossing later on Saturday to let some people out. Washington had been in touch with some Palestinian-Americans in Gaza who wanted to leave, the official said, adding it was not clear whether Hamas would let anyone reach the crossing.

Countries and aid agencies have sent supplies to Egypt but have so far been unable to bring them into Gaza. Israel says nothing can enter through Rafah without its coordination.

The Gaza Strip is already one of the most crowded areas in the world, and Israel's evacuation order for the northern half meant those fleeing south were forced to shelter with relatives and friends, in schools or in hastily rented apartments.

Israel says the order is a humanitarian gesture to protect residents from harm while it roots out Hamas fighters entrenched in Gaza City.

The United Nations says so many people cannot be safely moved inside the besieged enclave without causing a humanitarian disaster. It warned on Saturday of the threat of deadly water-borne disease without urgent deliveries of fuel to power Gaza's fresh water system.

Hamas has vowed to fight until the last drop of blood, and says the order to leave the north of the enclave is a trick to force residents to give up their homes. Gaza City mosques have blared calls telling people to stay.

An Israeli armoured personnel carrier (APC) heads towards the Gaza Strip border in southern Israel on Saturday, Oct. 14. AP-Yonhap

The Israeli military said on Friday tank-backed troops had mounted raids to hit Palestinian rocket crews and gather information on the location of hostages, the first official account of ground troops in Gaza since the crisis began.

The United Nations estimated that tens of thousands of Palestinians headed south from northern Gaza after the Israeli order on Friday, adding to 400,000 Gazans already displaced earlier in the week.

"We need immediate humanitarian access throughout Gaza, so that we can get fuel, food and water to everyone in need," U.N. Secretary General Antonio Guterres said on Friday. "Even wars have rules."

The United States has firmly backed its ally Israel, but has called on it to avoid civilian casualties. President Joe Biden said tackling the humanitarian crisis was a top priority.

"The overwhelming majority of Palestinians had nothing to do with Hamas and Hamas' appalling attacks," Biden said in a speech. "And they're suffering as a result as well."

U.S. Secretary of State Antony Blinken, on a lightning tour of the Middle East to rally allies, met Saudi Arabia's foreign minister in Riyadh and was due to travel to the United Arab Emirates. He has already visited Israel, Jordan and Qatar. (Reuters)

Palestinian rescue teams work under the rubble of a collapsed building following an Israeli strike, in Khan Yunis in the southern Gaza Strip on Oct. 14, as fighting between Israel and the Hamas movement continues for the eighth consecutive day. AFP-Yonhap