GAZA CITY (AFP) — At least 60 Palestinians were killed as Israeli forces pounded northern Gaza Sunday, sending thousands fleeing on day 13 of the deadliest assault on the enclave in five years.

Four more Palestinians were killed in an airstrike and 12 bodies were retrieved from the battered Shejaiya district, local medics said.

The airstrike hit a house in Bureij refugee camp in central Gaza, killing four people.

The intensity of the bombardment prevented emergency services from accessing the area and dead bodies lay in the streets as thousands fled in terror, an AFP correspondent reported.

Israeli officials said Shejaiya is a Hamas stronghold, and that 150 rockets had been launched from that area in the past two weeks, Israel’s Channel 2 said. Israeli military officials said Sunday that they had told civilians to leave the Shejaiya area days ago, ahead of IDF military action in a neighborhood regarded as a Hamas stronghold.

As UN chief Ban Ki-moon was to arrive in the region to add his weight to truce efforts, the Palestinian death toll spiraled past 400, with medics warning it could rise further from the ongoing bombardment of areas north and east of Gaza City.

“410 people have been killed since the war started and more than 3,020 people have been injured, most of them civilians,” deputy health minister Yussef Abu Rish told reporters at Shifa hospital in Gaza City.

As the scale of the casualties emerged, both Israel and Hamas agreed to a two-hour humanitarian ceasefire to enable ambulance crews to get in.

However, Israel later said the ceasefire had been breached and it would respond.

Until now, the Islamist Hamas movement, which is the dominant power in Gaza, had refused to yield in the face of the relentless air, sea and land attacks. It has pressed on with its own assaults which killed another two Israeli soldiers overnight, the army said.

As the warring sides showed no sign of giving up, diplomatic efforts to end the violence were to intensify Sunday with Hamas’s exiled leader Khaled Mashaal to meet Palestinian Authority President Mahmoud Abbas in Qatar to discuss an Egyptian truce proposal.

On the ground, the streets of the northern district of Shejaiya were filled with thousands of civilians fleeing for their lives after heavy shelling left casualties lying in the streets, an AFP correspondent reported.

Footage from the area showed vast clouds of black smoke billowing into the sky as the shelling continued and Gaza’s eastern flank burned.

Ambulances were unable to reach much of the area along the border because of heavy fire, and emergency services told AFP there were reports of dead and wounded trapped by the bombardment.

Emergency services spokesman Ashraf al-Qudra said at least 40 bodies had been retrieved from the eastern Shejaiya district, with another 380 people wounded.

Among the dead were women and children, as well as a Palestinian paramedic and a cameraman who were killed when the ambulance they were in was hit, with the ongoing fire hampering efforts to recover the bodies.

“He wasn’t a fighter, he was a fighter for humanity,” wailed one relative as the family buried him.

“He was an ambulance worker, did he deserve to die?”

A Palestinian man wheels an elderly woman holding a white flag forward as they flee their homes in the Shejaiya neighborhood of Gaza City, in the northern Gaza Strip, Sunday, July 20, 2014. (AP Photo/Hatem Moussa)

A Palestinian man wheels an elderly woman holding a white flag forward as they flee their homes in the Shejaiya neighborhood of Gaza City, in the northern Gaza Strip, Sunday, July 20, 2014. (AP Photo/Hatem Moussa)

Prime Minister Benjamin Netanyahu has placed the blame for civilian casualties squarely on Hamas, accusing the group of “using innocent civilians as human shields.”

At Gaza City’s Shifa hospital, Doctor Said Hassan told AFP that ambulances were unable to reach everyone, with many of the wounded walking hours to get treatment.

“This is the worst I’ve ever seen it,” said the doctor, who has worked at the hospital for eight years.

All around him, casualties were being brought in by the minute, some in ambulances, others in cars and trucks. Among them were children screaming in agony, many peppered with shrapnel wounds.

Fights broke out in the emergency room as hysterical parents banged on the walls in fear and sorrow.

“The shelling was non-stop, it was everywhere,” Sabah Mamluk, 40, told AFP.

“We ran into the streets and started to walk. It was terrifying,” she said.

“We got split up and found an ambulance that could bring us, but my husband is still there with the rest of the children and I can’t reach him by telephone.”

Early on Sunday, the army confirmed two more soldiers had been killed overnight, raising to seven the overall Israeli toll.

Four soldiers were killed on Saturday, among them two who died in a raid inside Israel. Another was killed by an anti-tank missile while the fourth died in a firefight, the army said.

Israel said its ground operation to destroy the network of tunnels used by Hamas to stage cross-border attacks was to “expand” later Sunday.

“This evening, the ground phase of Operation Protective Edge expands, as additional forces join the effort to combat terror in the Gaza Strip and establish a reality in which Israeli residents can live in safety and security,” the army said.

Earlier this week, the UN agency for Palestinian refugees expressed outrage after finding 20 rockets stored in one of its empty schools in Gaza.

So far, UNRWA has opened 55 of its schools to shelter those fleeing the most heavily bombarded areas, with more than 63,000 people taking refuge in them, the agency said.

“The number has tripled in the last three days reflecting the intensity of the conflict and the inordinate threats the fighting is posing to civilians,” spokesman Chris Gunness said in a statement.

Meanwhile, Hamas confirmed Mashaal had received an invitation for talks in Cairo on an Egyptian peace initiative. Egyptian officials were unable to confirm or deny the new invitation.

Earlier this week, an Egyptian truce proposal was accepted by Israel, but snubbed by Hamas, which said it had not been consulted.

Abbas and Mashaal were to meet in Doha later Sunday to discuss the Egyptian proposal, an official close to Abbas said.

The UN chief was also due in the Qatari capital.