Israel warns of new phase in war against Hamas, as Gaza civilians flee and Israeli troops gather near border

A new phase in Israel's deadly war against Hamas is coming, Israeli forces said on Saturday, warning that the past week of crippling airstrikes in Gaza could soon be followed by "significant ground operations."

Israeli troops and military equipment have massed at the border with Gaza as Israel prepares to ramp up its response to a deadly October 7 attack by the Islamist militant group Hamas, which controls the enclave. Warplanes continued to blast Gaza over the weekend, as civilians fled southward, following evacuation instructions by the Israel Defense Forces (IDF).

Several United Nations agencies have warned that mass evacuation under such siege conditions will lead to disaster, and that the most vulnerable Gazans, including the elderly and pregnant, may not be able to relocate at all. For days, Israel has cut off the Gaza population's access to electricity, food and water.

"The order to evacuate 1.1 million people from northern Gaza defies the rules of war and basic humanity," wrote Martin Griffiths, head of the United Nations Office for the Coordination of Humanitarian Affairs, in a statement late Friday. "Roads and homes have been reduced to rubble. There is nowhere safe to go."

Following an apparent explosion on Friday, extensive destruction could be seen on Salah Al-Deen street - a main route for evacuation - in videos authenticated by CNN. A number of bodies, including those of children, can be seen on on a flat-bed trailer that appears to have been used to carry people away from Gaza City.

It's unclear what caused the blast. CNN has reached out to the IDF for comment on any airstrikes in the same location.

Israeli military airstrikes have killed 70 evacuees and injured 200 more since the first evacuation order was issued Friday, Hamas' media office told CNN. According to the Palestinian Ministry of Interior and National Security, Palestinian medical services and civil defense crews were targeted by an Israeli strike at the site of a rescue operation in northern Gaza on Saturday.

The IDF has said that it targets locations associated with Hamas in the densely-packed enclave, and that Hamas leaders have already taken measures to protect themselves from airstrikes.

The Rafa border crossing, which connects Gaza with Egypt and is the only passage not controlled by Israel, could offer a sliver of hope for humanitarian aid eventually entering the territory, as well as for foreign nationals desperate to flee.

But the crossing appeared closed on Saturday when Palestinian-Americans gathered there at the suggestion of the US State Department.

"People are waiting at the Rafah crossing point but it's not open and there is no clear direction from the embassy," said Mai Abushaaban, a 22-year-old from Houston who is in contact with her family at the border.

"They told everybody to be here at 12, it's been two hours almost, nobody showed up, nobody is here to open the gates." Haneen Okal, a New Jersey resident, waiting with her three children, said.

CNN has reached out to the State Department and the US National Security Council for comment.

Canada had an agreement with Israel to get its citizens out of Gaza, but "there was violence around the Rafah Crossing and therefore the operation had to be canceled," Canada's Foreign Affairs Minister, Mélanie Joly, said.

Egyptian Foreign Minister Sameh Shoukry on Saturday said foreign nationals would be allowed to cross if protocols were followed on the Gaza side.

He also said Israeli aerial bombardment had rendered roads on the Gaza side of the crossing "inoperable."

"The Rafah crossing officially is open on the Egyptian side, it has been open all along. The problem with the roads is that it's been subject to aerial bombardment. Therefore, on the Gaza side the roads are not in a state that can receive the transit of vehicles," Shoukry told CNN's Wolf Blitzer.

Egypt has tried to ship humanitarian aid to Gaza but has not received the clearance to do so, he added.

A senior Jordanian official told CNN earlier this week that both countries were awaiting assurance that aid trucks would not be targeted by Israeli airstrikes.

More than 2 million Palestinians - including over a million children - live in the 140-square-mile Gaza Strip, one of the most densely populated places on Earth.

The territory has been under a land, sea and air blockade enforced by Israel since 2007, with more than half its residents living below the poverty line even before the latest conflict.

Saturday morning marked one week since Hamas' unprecedented and bloody attack on Israel, which killed more than 1,300 people and led to the capture of civilian and military hostages now believed to be held in Gaza.

The surprise attack, widely described as Israel's 9/11, saw waves of heavily armed Hamas fighters rampage through rural Israeli towns, kibbutzim and army bases.

In response, Israel ordered a "complete siege" of Gaza, including blocking food, water and fuel to the general population, while mounting its heaviest ever airstrikes on the enclave. International observers warn the cutoff will see Gaza civilians die by starvation, disease and lack of medical care for the growing numbers of dying and wounded.

At least 2,215 Palestinians have been killed in Gaza from Israeli strikes, the Palestinian Ministry of Health said in an update Saturday. That toll includes 724 children.

One overwhelmed hospital in Gaza told CNN that it had resorted to using ice cream trucks from local factories as makeshift morgues due to overflowing hospital mortuaries.

The IDF said Saturday that its fighter jets had struck operational headquarters used by Hamas militants, killing the head of the Hamas Aerial System in Gaza City, who the military claimed was "largely responsible for directing terrorists" during last week's attack on Israel.

Hostilities also spilled over between the Lebanese militant group Hezbollah and IDF forces on Saturday in the disputed Shebaa farms, near the Israel-Lebanon border. Israel said it returned fire after Hezbollah launched an attack on the territory - a disputed strip of land between Lebanon and Syria adjoining the Golan Heights, under Israeli control.

Images from Gaza have shown a mass rush toward the south of the coastal enclave beginning Friday.

Civilians crammed into cars, taxis, pickup trucks and even donkey-pulled carts. Roads were filled with snaking lines of vehicles strapped with suitcases and mattresses. Those without other options walked, carrying what they could.

Some healthcare facilities in the north of Gaza and Gaza City have said they will not be complying with Israel's evacuation orders, as these "threats effectively act as a 'death sentence' for the thousands of injured and patients housed within these facilities."

Others have stayed put in their homes, telling CNN they felt nowhere is secure.

The IDF said Saturday it would allow people to move south "for their own safety" on specified streets of Gaza during a six-hour window, but it is unclear how widely the messaging was received on the ground, given the widespread electricity and internet blackout.

The IDF did drop leaflets about the announcement in addition to other platforms, IDF spokesperson Maj. Doron Spielman said.

However, multiple people - including a United Nations Relief and Works Agency school official, a paramedic and a journalist on the ground - all told CNN they were unaware of the advisory.

Even before the evacuation warning, more than 400,000 Palestinians had already been forced to flee their homes due to airstrikes.

CNN's Paul Murphy, Sharif Paget, Helen Regan, Caitlin Hu, Mohammed Tawfeeq, Akanksha Sharma, Nadeen Ebrahim, Nada Bashir, Ali Younes, Rhea Mogul, Yahya Abou-Ghazala, Ben Wedeman, Catherine Nicholls, Laura Paddison, Akanksha Sharma, Tim Lister, Hadas Gold and Jessie Gretener contributed to this report.