The UN agency for Palestinian refugees said Tuesday it had found unexploded 1,000-pound bombs inside schools after Israel pulled troops out of southern Gaza's main city Khan Yunis.
The Israeli army has carried out relentless air strikes and bombardments in Gaza since Hamas militants attacked Israel on October 7.
UN agencies led an "assessment mission" in Khan Yunis after Israeli forces withdrew from the embattled city last week, UNRWA said.
It found "significant challenges in operating safely due to the presence of unexploded ordnance (UXOs), including 1,000-pound bombs inside schools and on roads".
"Thousands of internally displaced persons (IDPs) require a range of lifesaving assistance, including health, water and sanitation, and food," it said.
Earlier this month, the United Nations said it would take "millions of dollars and many years to decontaminate the (Gaza) Strip from unexploded munitions".
"We work off the rule of thumb that 10 percent of ordnance doesn't function as designed," UN Mine Action Service chief Charles Birch said in a statement earlier this month.
"We estimate that, to begin the clearance of Gaza, we need around $45 million."
The October 7 Hamas attack that triggered the war resulted in the deaths of 1,170 people in Israel, mostly civilians, according to an AFP tally of Israeli official figures.
Israel's retaliatory offensive has killed at least 33,843 people in Gaza, mostly women and children, according to the health ministry in the Hamas-run territory.