WADI GAZA - Evacuation orders from Israel’s military have forced hundreds of thousands of people to flee south from their homes in northern Gaza since Friday, the largest wave of civilian displacement in a week of war with Hamas, according to the United Nations, even as others refused to leave, fearing that escape routes are too dangerous.

The main roads running north to south were crowded for a second day Saturday after the Israeli military announced a six-hour window for civilians to move along designated streets to parts of Gaza south of the Wadi Gaza wetlands here. In some areas traffic came to a standstill with trucks, buses, overpacked cars and people on foot all crowding on to the same narrow roads to head south.

But many civilians, including hospital staff, are refusing to leave. Ahmed Okal, 43, who lives in Gaza City’s Zaitoun neighborhood, said he didn’t trust that civilians traveling south wouldn’t be targeted with airstrikes.

“I am definitely afraid, very afraid, but I will not risk the lives of my wife and children on the way to the south,” he said, referring to reports that some of those fleeing were killed in an airstrike. “Let us die inside our homes,” he said. “The road is dangerous.”

Rawan Abu Hamda, 41, also from Gaza City, started out on an evacuation route but quickly returned home after hearing reports of a strike that hit civilians on the road. She said hundreds of other families have also stayed in her neighborhood, many sheltering near al-Shifa hospital, in hopes the building won’t be hit by airstrikes - although the ceiling of the nursery department collapsed on Oct. 9 after shelling nearby.

Reports emerged Friday of a strike on cars packed with fleeing civilians. The Washington Post verified a graphic video of the aftermath recorded along Salah Al-Deen Road. The video shows bodies, including several young children, strewn along the road as black smoke rises from vehicles engulfed in flames. On the north-facing side of the road, bodies are laid out amid personal belongings, including a bicycle, on flatbed trailers attached to a truck.

The Palestinian Ministry of Health said 40 people injured in the attack were taken to al-Shifa hospital. Israel’s military said they could not confirm reports of a strike at the location.

The video was first geolocated by open-source researchers Chris Osieck and Gabòr Friesen and confirmed by The Post.

The Israel Defense Forces said Hamas is setting up checkpoints, preventing people from evacuating Gaza City and the north. But civilians who fled to the south since Friday told The Post they did not see any Hamas fighters in the streets.

Hamas has called on civilians to stay in their homes. Israel first issued the order to evacuate Gaza City and the north on Friday. More than a million people live in the area under the order.

“They have time to move south, they have to start moving,” Israel Defense Forces spokesman Richard Hecht said Saturday morning. “We understand this will take time,” he added, but declined to say if, or for how long, the deadline for the evacuation, which has passed, would be extended.

“We’re not going to do carpet bombing of Gaza. Every target will have intelligence behind it,” Hecht said. Israeli officials have said the aim of the war in Gaza is to dismantle Hamas’s military and political capabilities.

U.S. officials said they negotiated a temporary opening at the Rafah border crossing between Gaza and Egypt for American citizens seeking to flee, but a Palestinian border authority spokesman and witnesses in the area said the crossing remains closed.

The evacuation orders appear to signal Israel plans to significantly escalate its war against Hamas ahead of, or in tandem with, an expected ground invasion. But human rights groups and aid organizations are warning that civilians must continue to be protected, regardless of the orders to move out.

“Many persons particularly pregnant women, children, older people and people with disabilities, will not be able to flee the area,” the United Nations agency for Palestinian refugees said in a statement. “They have no choice and must be protected at all times.”

Human Rights Watch said the Israeli order is “not an effective warning.”

“The roads are rubble, fuel is scarce and the main hospital is in the evacuation zone,” said Clive Baldwin, a senior legal adviser at Human Rights Watch. “This order does not alter Israel’s obligations to never target civilians and take all measures it can to minimize harm.”

The al-Quds hospital in Gaza City also received orders to evacuate by Saturday afternoon, but the Palestinian Red Crescent is refusing to shutter the facility, according to a statement from the group.

The hospital is providing care to a “large number” of patients, including children in incubators, and people in the intensive care unit, the Red Crescent said in a statement. The group said tens of thousands of civilians remain in the area and hundreds of people are also sheltering at or near the hospital

Red Crescent teams at the hospital “will continue to provide essential lifesaving services to the people remaining,” and the organization will “continue the provision of services to the sick and wounded.”

George reported from Jerusalem and Brown reported from Washington. Joyce Lee and Samuel Oakford in Washington contributed to this report.