The ordnances pose “severe risks to civilians, especially for children," spokesperson Stephane Dujarric said at a news conference.
Dujarric said a UN team conducted an assessment in Khan Younis on Wednesday and reported "widespread destruction of every building" they visited.
Noting damages on the roads in Khan Younis, Dujarric said, “The UN team found unexploded 1,000-pound bombs lying on the main intersection and inside the schools."
On the Israeli airstrike killing family members of Ismail Haniyeh, the head of Hamas’ political bureau, Dujarric avoided direct comments but said, "We have spoken out clearly since the beginning of this conflict, highlighting the toll that children are bearing in an overwhelming way in this conflict."
The Israeli war on Gaza has killed more than 33,500 people and injured over 76,000 others, in addition to causing mass destruction, displacement and bringing its population of more than 2 million to the verge of famine.
Israel is accused of genocide at the International Court of Justice, which has ordered Tel Aviv to stop genocidal acts and take measures to guarantee that humanitarian assistance is provided to civilians in Gaza.