The rush to leave came after the Israeli military urged around 1.1 million Gazans living in the north of the Palestinian territory to flee "for their own safety and protection", ahead of an expected ground incursion.
Some were in cars, many others were on foot as they sought to make the trip to the south of the densely populated territory that is home to 2.4 million people on its 362 square kilometres (140 square miles).
But for thousands like Umm Hossam, they are left with one crucial question: "Where to go?"
"How long will the strikes and death last? We have no homes left, every area of Gaza is under threat," said the 29-year-old, her face streaked with tears.
"We call on Arab countries to protect us. Where are the Arabs? Enough! Enough!" she cried.
The majority of Gazans have been boxed into the small territory under a strict air, land and sea blockade imposed by Israel since 2006.
After gunmen from Hamas -- which has ruled the Gaza Strip since 2007 -- stormed across the border into Israel on Saturday, killing more than 1,300 people, Israel has imposed a "complete seige" on Gaza, cutting off all water, electricity and food supplies.
Israel has also been relentlessly bombing Gaza in airstrikes that have so far claimed about 1,800 lives.
Hossam told AFP she had taken cover at a relative's house in the north of the enclave before Israel's order to evacuate came.
She had hid out there for three days after her own neighbourhood northwest of Gaza City was struck.
"They told me the house was completely destroyed," she said.
The United Nations has urged Israel to rescind its call for Gazans to evacuate.
"The United Nations considers it impossible for such a movement to take place without devastating humanitarian consequences," Stephane Dujarric, spokesman for the UN secretary-general, said on Thursday.
In the meantime, Israeli warplanes have dropped thousands of leaflets on Gaza, urging residents to head south, though the timeline for the evacuation is unclear after the army acknowledged the process may "take time".
Hamas has rejected the evacuation call, but did not actively block the thousands who are moving south, many with their belongings packed in plastic bags.
Displaced 'yet again'
Still, many have chosen to remain in the north of the strip, amid the absence of transportation, and moreover nowhere else to go.
"This is a brutal enemy and what they want is to scare people into displacement," a resident, Abu Azzam, told AFP. "But, God willing, we will remain steadfast in the face of any displacement."
Mohamed Khaled, 43, similarly said he would stay. "What does the world want from us? I am a refugee in Gaza and they want to displace me yet again?
"What will we do in Rafah?" he asked, referring to the city 40 kilometres (24 miles) south of Gaza City. "Sleep on the streets with our children? We won't do it. I don't want this humiliating life."
There have been repeated calls for the creation of humanitarian corridors into Gaza, particularly through the Rafah crossing to Egypt -- the only one not controlled by the Israeli military.
But Egyptian President Abdel Fattah al-Sisi has said it is necessary for Gaza residents to "remain steadfast on their land", warning that any mass displacement of Gazans would spell the end of the Palestinian cause.
In Al-Shati refugee camp west of Gaza City, Mohamed Abu Ali stands in front of an office for the UN Palestinian refugee agency (UNRWA).
"Today, we don't know, where do we go?" the 24-year-old said. "There is nowhere safe. We went to the United Nations for refuge. Israel is committing massacres today against civilians and our children are under the rubble.
"We don't know what to do. We have no food and no water. I ask the UN in front of its headquarters: Where do we go?"
