Tank shelling on a UN shelter on Wednesday killed nine people in Gaza's main southern city of Khan Yunis, said the Gaza head of the UN agency for Palestinian refugees.
"Two tank rounds hit building that shelters 800 people - reports now 9 dead and 75 injured," Thomas White, UNRWA's Gaza director, said on X, formerly Twitter.
Teams from UNRWA and the World Health Organization were trying to reach the shelter, which has been blocked for two days, White said.
Earlier he said the UNRWA training centre had been hit, with "buildings ablaze and mass casualties".
"There was an estimated 10,000 people sheltering at that facility," James McGoldrick, interim UN humanitarian coordinator for the Palestinian territories, told reporters Wednesday by video link.
Footage aired on Al Jazeera Arabic showed fire raging and thick plumes of smoke rising out of the building.
Philippe Lazzarini, the head of UNRWA, said on Tuesday the same shelter had been hit during military operations.
At least six displaced people were killed and "many more injured" in the fighting, he said.
Intense fighting was also reported Wednesday close to hospitals in Khan Yunis.
The Hamas government media office said "dozens of Israeli tanks are surrounding Nasser hospital from all sides, except for a corridor for displaced people to leave."
The Israeli army said Tuesday it had "encircled" Khan Yunis, which has become the epicentre of recent fighting.
The Gaza war began with Hamas's unprecedented October 7 attacks, which resulted in the deaths of about 1,140 people in Israel, mostly civilians, according to an AFP tally based on Israeli official figures.
Militants also seized 250 hostages, and Israel says around 132 remain in Gaza. That number includes the bodies of at least 28 dead hostages, according to an AFP tally based on Israeli figures.
In response, Israel has carried out a relentless military offensive that has killed at least 25,700 people in Gaza, about 70 percent of them women and children, according to the health ministry in the Hamas-run territory.