Six United Nations workers and several others were killed in an Israeli air strike on a school compound sheltering hundreds of displaced Palestinians in central Gaza.
The Gaza Government Press office reports the total to be 18, while officials from Awda and al-Aqsa Martyrs hospitals said at least 14 people were killed.
People were seen collecting body parts in plastic bags. Local media reported at least 22 people were also injured.
At least 220 UNRWA staff have been killed so far in the conflict, according to the UN.
Mr Deere said the IDF knows the GPS locations of every UNRWA facility, which are updated daily, and all movements are coordinated with them.