The U.N. agency for Palestinian refugees (UNRWA) chief Philippe Lazzarini urged countries to support an independent probe into Israel's killings and detentions of its staff and damage to its compounds in Gaza.
UNRWA has accused Israel of targeting its facilities during more than seven months of conflict in the Gaza Strip and said 182 of its staff there had been killed and more than 160 of its shelters hit, resulting in the deaths of hundreds of people fleeing Israeli bombardment.
After briefing U.N. member states in Geneva, UNRWA Commissioner-General Philippe Lazzarini told reporters he wanted the countries to back an independent investigation "to look into this blatant disregard of the United Nations in order to avoid that this becomes also in the future the new standard."
Israel blocked Lazzarini from entering Gaza last month, and he plans to visit again on Sunday. He voiced hope that Israel would let him in.
UNRWA is the biggest humanitarian aid provider in Gaza where its 13,000 staff there also run schools and social services for the refugees who make up the majority of Gazans.
Health authorities in Gaza say more than 34,000 Palestinians have been killed in Israeli attacks.
Israeli Prime Minister Benjamin Netanyahu, who is accused of carrying out a genocide in Gaza, has called for UNRWA to be shut down, claiming that it seeks to preserve the issue of Palestinian refugees.
Most countries unblock funding
A review of the agency's neutrality said Israel had yet to provide evidence for its accusations that a significant number of UNRWA staff were members of terrorist groups and Lazzarini said that all but a handful of countries had now unblocked funds they had paused after the Israeli allegations.
He listed those still withholding funds as the United States, Britain, Austria and his native Switzerland.
The Swiss lower house's foreign affairs committee on Tuesday narrowly voted to partly unblock financial aid to UNRWA solely for humanitarian ends, a step that needs further parliamentary approval.
Some $267 million in total remains blocked, Lazzarini said, based on a tally of countries' prior commitments. The agency has raised $115 million in private funding, he added.
Another U.N. investigation into the allegations against UNRWA staff members is still under way.
Food and other humanitarian aid supplies to Gaza have improved in April, but there is still far from enough to reverse the trend towards famine, he said.
"We are engaged in a race against the clock to reverse the spreading of hunger and the looming famine especially in the northern part," he said.