At least 20 people have been killed, including five children, and dozens are missing after a war-damaged building collapsed in the Gaza Strip, according to rescue teams.

Videos showed the search for bodies and survivors continuing in the rubble of the six-storey building in the Tal al-Hawa area of Gaza City.

Locals said some 10 families had been living in the apartments despite warnings that they were unsafe.

Members of the Hamas-run Civil Defence rescue service said they had initially been working with "empty hands" due to tight Israeli restrictions on equipment allowed into Gaza. However, they have since been able to borrow some heavy machinery from UN agencies and Egyptian relief workers.

"We are still hearing voices from under the rubble, so there is still hope to find people," said Raed al-Dahshan, the director of the Civil Defence in Gaza City.

He added: "The limited availability of shelter options forced residents to move into this building, believing it was safe. However, at one point it collapsed entirely, tragically crashing down on people as they slept."

The head of the United Nations Development Programme (UNDP) Gaza office, Alessandro Mrakic, told reporters at the scene that between 70 and 100 people were believed to be trapped under the rubble.

"The situation, as you see, is tragic because we don't have the equipment and machinery that is needed. There are actually people digging with their bare hands," he said.

Mrakic also warned that approximately 400 other war-damaged buildings across Gaza were at imminent risk of collapse, particularly as winter approaches.

"We need support, most importantly with machinery, equipment, among others. Our colleagues here don't have [engine] oil and spare parts to continue to work with all the equipment that is still in Gaza."

The UN's humanitarian relief co-ordinator, Ramiz Alakbarov, also called on Israeli authorities to approve deliveries of heavy machinery for rescue operations, as well as tents, tarpaulins and other non-food items for displaced people ahead of the winter rains.

More than 80% of all structures in Gaza have been destroyed or damaged during the war between Israel and Hamas, according to the UN.

More than 1.9 million people - about 90% of the territory's population - have been displaced, many of them multiple times, and 1.2 million of them are currently living in tents or makeshift shelters, according to the UN.

The UN's humanitarian office says the humanitarian situation in Gaza remains dire despite the ceasefire agreed last October, as Israeli air strikes and other attacks continue to hit populated areas, causing casualties and property damage and driving further displacement.

On Tuesday, Israeli air strikes killed at least five Palestinians, including two children and a Hamas commander, according to health officials and Hamas sources.

The Israeli military said it killed a Hamas commander in southern Gaza and another fighter in the north. In both cases, a child was also reportedly killed.

Separately, the British charity Medical Aid for Palestinians said that a patient was killed by an Israeli drone at a health centre it supports in Jabalia in northern Gaza. An Israel Defence Forces (IDF) spokesperson told the BBC it was not aware of such an incident.

The Gaza war was triggered by the Hamas-led attack on southern Israel on 7 October 2023, when about 1,200 people were killed and 251 others were taken hostage.

Since then, more than 73,790 people have been killed in Gaza, according to the territory's Hamas-run health ministry, whose figures are considered reliable by the UN.