The United Nations human rights office said it had received reports that Israeli troops "summarily killed" at least 11 unarmed Palestinians in a possible war crime in Gaza.
The OHCHR office in the West Bank city of Ramallah said the killings were alleged to have been carried out in the Rimal neighbourhood of Gaza City this week.
It said on Wednesday it had received "disturbing information alleging that Israeli Defence Forces (the Israeli army) summarily killed at least 11 unarmed Palestinian men".
The incident "raises alarm about the possible commission of a war crime", it said, adding the men were killed in front of their family members.
The report said troops also ordered women and children into a room "and either shot at them or threw a grenade into the room, reportedly seriously injuring some of them, including an infant and a child".
An Israeli official rejected the claims as "nothing but blood libel".
"The latest claims are yet another example of the partisan and prejudiced approach against Israel that the OHCHR has adopted for years now," the official said on condition of anonymity.
The Israeli army did not immediately comment.
Israeli troops have previously been accused of deliberately targeting and killing civilians, according to the office.
The war between Israel and Hamas, which rules the Gaza Strip, began after the Islamist group attacked southern Israel on October 7 and killed around 1,140 people, according to an AFP tally based on Israeli figures.
Israel's retaliatory offensive in Gaza has killed at least 20,000 people, most of them children or women, according to the Hamas government.
Israel strike kills head of Gaza side of border crossing: Hamas
An Israeli strike killed the head of the Palestinian side of the Kerem Shalom border crossing on Thursday, Hamas authorities in the Gaza Strip said.
Crossing director Bassem Ghaben and three other people were killed as Israeli aircraft targeted the infrastructure, the crossings authority and the health ministry in the Hamas-ruled Palestinian territory said.
The Israeli army and COGAT, the defence ministry body responsible for Palestinian civil affairs, did not immediately respond to requests from AFP for comment.
After weeks of pressure, Israel approved the temporary reopening of the Kerem Shalom crossing on Friday to enable aid to be delivered directly to Gaza, rather than through the Rafah crossing from Egypt.
United Nations official Tor Wennesland said Tuesday that Israel's "limited" steps to allow aid into Gaza were "positive, but fall far short of what is needed to address the human catastrophe on the ground".
The UN estimates 1.9 million of Gaza's 2.4 million residents have been displaced and concerns are growing about the ability of aid groups to help.
The war began when Hamas attacked Israel on October 7, killing around 1,140 people, mostly civilians, and abducting about 250, according to an AFP tally based on Israeli figures.
The Hamas government's media office said Wednesday that Israel's retaliatory assault had killed at least 20,000 people in the Palestinian territory, with 8,000 children and 6,200 women among the dead.