The Israeli army is killing Palestinians in Gaza at a rate far greater than recent major conflicts in Ukraine, Sudan, and Yemen, Oxfam said on Thursday.
The anti-poverty charity said 250 Gazans are being killed daily on average, adding that many other lives are threatened by hunger, disease, and cold.
It comes as the International Court of Justice hears evidence from South Africa and Israel on Thursday and Friday in Pretoria's case accusing the Israeli government of genocide in the Palestinian territory.
"The scale [of] atrocities that Israel is visiting upon Gaza are truly shocking," said Oxfam's Middle East director Sally Abi Khalil.
"For 100 days the people of Gaza have endured a living hell. Nowhere is safe and the entire population is at risk of famine.
"It is unimaginable that the international community is watching the deadliest rate of conflict of the 21st century unfold, while continuously blocking calls for a ceasefire."
Oxfam used publicly available data to determine that the average rate of killings per day in Gaza is significantly greater than any other recent major armed conflict.
This includes Syria, where the NGO said there were 96.5 deaths a day, Sudan – where the rate was 51.6 – and Ukraine, where it was 43.9.
Israel's war on Gaza began on 7 October and has so far killed almost 23,500 people.
The war has seen hospitals, ambulances, residential buildings, and places of worship attacked.
Israel has also tightened its crushing years-long siege of Gaza.
"Israel's total blockade of the Gaza Strip is restricting life-saving aid, including food, medical supplies, and water and sanitation facilities," Abi Khalil said.
"On top of the already horrific death toll, many more people could die from hunger, preventable diseases, diarrhoea and cold. The situation is particularly worrying for children, pregnant women and those with existing medical conditions.
"The only way to stop the bloodshed and prevent many more lives being lost is for an immediate ceasefire, for hostages to be released and for crucial aid supplies to be allowed in."