At least 274 people were killed during the raid on Saturday, according to Palestinian health officials.
The rare daylight raid was carried out by heavily armed Israeli special forces with air support.
More than 600 people were injured in the raid, including children and women, according to Palestinian officials. The influx of patients since the raid has overwhelmed hospitals in the enclave, which were already operating with limited supplies of medicine, food and fuel.
Jeremy Laurence, a spokesman for the office of UN High Commissioner for Human Rights Volker Turk, said on Tuesday that the office is “profoundly shocked” at the impact of the Israeli assault on civilians.
“The manner in which the raid was conducted in such a densely populated area seriously calls into question whether the principles of distinction, proportionality and precaution – as set out under the laws of war – were respected by the Israeli forces,” he said in a statement.
Laurence said Turk welcomed the UN Security Council resolution passed on Monday to endorse a US-backed Gaza ceasefire proposal and said all parties must ensure the “unfettered flow of humanitarian aid”.
At least 37,164 people have been killed and 84,832 injured since the start of the war on October 7, according to the Palestinian Ministry of Health in Gaza.