The UN humanitarian aid chief has defended the organization"s use of casualty figures in the Gaza war in response to sharp criticism by Israel. Martin Griffiths told the BBC the UN was "very cautious" in its approach. Israel earlier said a recent reduction in UN estimates of killed Palestinian women and children suggested it had relied on false data from Hamas. On 6 May, the UN said 69% of reported fatalities were women and children. On 8 May, it said this figure was 52%. The UN"s Office for the Coordination of Humanitarian Affairs (OCHA) says incomplete information has led to the revision. The UN also says it is now relying on figures from the Hamas-run health ministry in Gaza, rather than from the Hamas-run Government Media Office (GMO). Speaking to the BBC"s Today program, Griffiths said: "Gaza is a war zone and the collection of data and statistics, while admirable and necessary, is first of all secondary to actually delivering some aid and, secondly, very difficult in cases of insecurity and violence. "So... be realistic, please, about what"s possible in the middle of what we"re seeing in Gaza. I think we are very cautious about these figures and I think it"s not right to blame the messenger who is trying to get truth out of what is a very, very complicated situation." At the start of the war last October, the Hamas-run health ministry only reported deaths for which details had been registered in hospitals, whereas from November, the GMO included an additional category of deaths recorded in "reliable media reports". On 6 May, OCHA reported 34,735 deaths — of which there were more than 9,500 women and more than 14,500 children, citing the GMO as its source. Then two days later, the UN released a further report, switching its sourcing to the health ministry. The result of this was that although the overall recorded death toll was almost unchanged (34,844), the number of registered deaths of women (4.959) and children (7,797) as of 30 April had both fallen significantly. This difference was because those individuals with incomplete information were not included in the demographic breakdown. Reacting to the change in the official UN estimates, Israeli Foreign Minister Israel Katz called on the UN Secretary General Antonio Guterres to step down. "The miraculous resurrection of the dead in Gaza. The UN had reduced its estimate of women and children killed in Gaza by 50% and claims that it relied on data from the Hamas Ministry of Health," Katz wrote in a post on X on Monday. "Anyone who relies on fake data from a terrorist organisation in order to promote blood libels against Israel is antisemitic and supports terrorism. @antonioguterres, resign!" Israel began its military campaign in the Gaza Strip in the wake of Hamas"s attacks on 7 October, in which 1,200 people — mostly civilians — were killed, and 252 others were taken hostage. — BBC