Footage from the scene shared online and verified by Al Jazeera on Thursday showed local residents trying to extinguish a fire and rescue survivors as black smoke rises from one of the buildings.

Two adjacent homes belonging to the Abu Dhbaa and Ashour families were obliterated in the attack on the city, where tens of thousands of displaced people have sought shelter since a weeklong truce collapsed in early December.

Displaced people have been sleeping in makeshift shelters and in the streets after evacuating from the north and from other areas of southern Gaza that had previously been deemed safe by the Israeli army.

“It was difficult because of the dust and people’s screams. We went there, and we saw our neighbour who had 10 martyrs,” said Fadel Shabaan, a resident who rushed to the area after the bombing.

“This is a safe [refugee] camp. There is nothing here. The children play football in the street,” he told the news agency Reuters.

Gaza health authorities said 26 people were killed in the attack. Gaza’s Ministry of Health said on Thursday that at least 179 people had been killed and 303 wounded in Israeli attacks over the past day, bringing the death toll in Gaza since the war began on October 7 to 18,787 with 50,897 injured.

Footage verified by Al Jazeera shows relatives mourning by the shrouded bodies of at least 20 people.

A member of the Ashour family said she lost her mother, two brothers, their wives and their children.

“I have a niece who is still under the rubble,” she said. “We had displaced people. One of them was our cousin who was displaced from the north. Our neighbour and his grandmother who were displaced from Beit Lahiya were killed too.”

Another member of the Ashour family said there were more than 50 people inside the four-storey building.

“They were people from Beit Lahiya, Jabalia, al-Saftawi and Nuseirat,” she said. “We lost [an] old lady, a five-month pregnant lady, her little boy and her husband, … my brother, his son and his wife.”

Fighting rages across Gaza

Two weeks after the truce collapsed, the war has entered an intense phase with fighting now raging across the entire Palestinian enclave and international organisations warning of a worsening of the humanitarian catastrophe there.

Israel has brushed off calls for a ceasefire, including a resolution at the UN Security Council blocked by a US veto last week and another that passed overwhelmingly in the General Assembly this week.

Despite Israel’s pledges to reduce harm to civilians, it has extended its ground campaign from the north to the south this month, leaving no part of the enclave unscathed. It says it is offering warnings where it can before attacking an area.

In the main southern city, Khan Younis, where advancing Israeli forces reached the centre this week, a whole city block was bombed to dust overnight. Although most people had fled after Israeli warnings, neighbours digging in the rubble with a hand shovel afterwards said they believed four people were under the debris. One body had been recovered.

In the north, including the ruins of Gaza City, fighting has escalated since Israel announced that its troops had largely completed their military objectives last month.

In Jabaliya also in the north, Gaza’s Health Ministry said Israeli forces had stormed a hospital, detaining and abusing medical staff and preventing them from treating a group of wounded patients, at least two of whom had died.

Twelve children were in the intensive care unit, where the electricity had been cut and there was no milk, ministry spokesperson Ashraf al-Qudra said.

Israel’s military said Palestinian fighters had been operating inside the hospital, 70 of whom had surrendered there “with weapons in hand” and were now undergoing interrogation.

Washington has provided diplomatic cover for its ally but expressed increasing alarm over civilian deaths. US President Joe Biden, whose government has provided Israel with billions of dollars in military aid, delivered his sharpest rebuke of the war on Wednesday. He said Israel’s “indiscriminate bombing” of Gaza was eroding its international support.

White House National Security Adviser Jake Sullivan, who arrived in Israel on Thursday, will discuss with the Israelis the need to be more precise with their strikes, spokesperson John Kirby said.

Up to 45 percent of the 29,000 air-to-ground munitions that Israel has dropped on Gaza since October 7 have been unguided “dumb bombs”, according to a US intelligence assessment reported by CNN.

Agriculture Minister Avi Dichter, a member of Israel’s security cabinet and Prime Minister Benjamin Netanyahu’s Likud party, rejected Biden’s characterisation of Israel’s strikes as indiscriminate.

“There is no such thing as ‘dumb bombs’. Some bombs are more accurate. Some bombs are less accurate. What we have is mostly pilots who are precise,” he told Army Radio. “There is no chance that Israel’s air force or other military units fired at targets that were not terror targets.”

“[Sullivan] will likely point to the UN General Assembly vote in favour of a ceasefire earlier this week, but we have already heard from Netanyahu and [Israeli Defense Minister Yoav] Gallant that this war will be conducted the way they want,” Al Jazeera’s Alan Fisher said, reporting from occupied East Jerusalem.

Netanyahu promised to carry on the war “until victory, nothing less than that”, and Foreign Minister Eli Cohen has said the war would continue “with or without international support”.

The United Nations estimated 1.9 million out of Gaza’s 2.3 million people have been displaced.

The head of the UN Relief and Works Agency for Palestine Refugees, Philippe Lazzarini, said on Wednesday that Palestinians in Gaza were “facing the darkest chapter of their history”.

He said they are “now crammed into less than one-third” of the territory and hinted there could be an exodus into Egypt, “especially when the border is so close”.

Cold wintery rain has lashed the makeshift tents where the displaced struggle to survive without sufficient food, drinking water, medicines or fuel for cooking.