Children are among the dead after an Israeli airstrike on a block of flats in a Gaza refugee camp killed at least 33 people, according to Hamas-run health authorities.
The attack – which Israel said targeted a “senior terrorist” but may have caused a secondary blast – came hours after the US national security adviser raised hopes of a ceasefire deal.
More than 80 people are said to be missing after the attack in Nuseirat camp on Thursday night.
Palestinian medics also reported more than 40 people, most of them children, were receiving treatment at two hospitals, according to the Reuters news agency.
Images from the scene show a collapsed building, which Reuters reports was a post office used as a shelter.
The al Aqsa Hospital said the attack also damaged several nearby houses.
Nuseirat is one of eight historic camps in Gaza, which were originally for Palestinian refugees from the 1948 war leading to the establishment of Israel.
Now it is part of a dense urban area crowded with displaced people from across Gaza.
The Israel Defence Forces (IDF) said it targeted “terror infrastructure” in the Nuseirat area, singling out a “terrorist responsible for leading terror attacks against Israeli civilians”.
But an “initial inquiry” by the IDF suggests a nearby building was likely damaged “due to the presence of numerous weapons in the structure where the terrorist was located”.
“Secondary explosions were identified,” the IDF said. It added that details and the number of casualties are under review.
“This is another example of the Islamic Jihad’s systematic exploitation of civilian infrastructure and the civilian population as a human shield for its terrorist activities,” the IDF added.
Earlier on Thursday, President Joe Biden’s national security adviser Jake Sullivan, who is in Israel to try to secure a ceasefire, said he is hopeful of a deal.
“I wouldn’t be here now if I didn’t think this thing was just waiting until after 20 January,” he said, referring to Donald Trump’s inauguration.
More than 44,800 Palestinians have been killed by Israeli forces in Gaza since the latest war began last year, according to the Hamas-run health ministry in the territory.
The health ministry says more than half of the dead are women and children. Its casualty figures do not differentiate between militants and civilians.