By Ibrahim Dahman, Abeer Salman and Billy Stockwell, CNN

(CNN) — More than 20 people, including several children, have died after a war-damaged residential building in Gaza City collapsed early Wednesday morning, local authorities said, with dozens more feared trapped under layers of rubble.

Dr. Mohammed Abu Salmiya, the director of Al-Shifa hospital, told CNN at least 21 people had been killed in the disaster, including eleven children, while many others had been injured.

Search and rescue operations are underway at the site of the collapsed Al-Sa’ada building in the city’s Al-Rimal neighborhood, where around 100 people are missing, according to Gaza’s Civil Defense agency.

The building, which is six stories high with four apartments on each floor, was targeted by Israeli airstrikes at the beginning of the war in Gaza following the October 7 attacks in 2023, the Civil Defense agency said.

Around 80% of all structures in Gaza have been damaged since the conflict began, with two-thirds of them destroyed, according to the UN, leaving Palestinians struggling to find safe shelter amid ongoing Israeli airstrikes and the threat of unexploded ordnance.

The demand for shelter is high, especially as winter approaches, with around 1.9 million Palestinians in Gaza – or about 90% of the population – displaced during the war, the UN said. Many people in the territory have been displaced several times.

Hamas’ media office in Gaza said the building fell onto “dozens of displaced families who had been forcibly driven to seek shelter there, amid the complete absence of alternative and safe places of refuge.”

It accused Israel of obstructing rescue efforts by “maintaining its categorical refusal to allow the entry of sufficient equipment, machinery and rescue supplies needed to respond to such disasters.” Israel restricts the entry of what it calls “dual use goods” into Gaza, including heavy equipment, which it says Hamas could repurpose for military use.

Ramiz Alakbarov, the UN’s humanitarian coordinator for the Occupied Palestinian Territory, called for “urgent approvals” to be granted for the entry of heavy machinery, engine oil and fuel into Gaza.

“No one should have to risk their life simply to find a safe place to shelter,” he said Wednesday.

‘A tragic, painful scene’

Gaza’s Ministry of Housing said Wednesday around 3,000 buildings in the territory have been classified as “dangerous” or at risk of collapse, after previous Israeli strikes caused structural damage and cracks.

It said the damage poses a “direct threat to the lives of thousands of families,” and called for an immediate regional and international response.

“Since midnight in Gaza City a tragic, painful scene has unfolded: a brutal humanitarian event, as you can see in front of you under this residential building, where dozens of innocent people were trapped,” Civil Defense spokesman Mahmoud Basal said Wednesday.

“People woke up at 3 a.m. to screams and the crying of children who were inside after the building completely collapsed on them,” he added. “We warn of further collapses like this incident in the Gaza Strip, in the areas where citizens are now sheltering.”

No significant reconstruction has taken place in Gaza since a fragile ceasefire deal was agreed last October between Hamas and Israel. The UN reported in late August that the percentage of damaged buildings in the territory has continued to increase since the ceasefire.

Meanwhile, concrete progress from US President Donald Trump’s Board of Peace, created to advance the US-brokered ceasefire agreement, remains elusive, following recent criticism from Israel.

This is a developing story and will be updated.