In Yemen alone, 73 UN staff remain detained by the de facto Houthi authorities.
Israel has prohibited UNRWA from operating in the Gaza Strip since January.
He called for an immediate ceasefire in Gaza and a return to negotiations to end the war.
Israel alleged that UNRWA employees were involved in a Hamas attack on October 7, 2023, a charge vehemently denied by the UN agency.
“This is the moment for voices of reason to prevail, for solutions that will deliver justice and make space for compassion, healing and truth-telling,” Mr Türk said.
Israel accuses UNRWA, which has supported Palestinians since 1949, of employing staff who participate in terrorist activity.
“This cannot happen soon enough,” she said, speaking on behalf of the UN secretary-general António Guterres on Monday.
The U.S. on Wednesday vetoed a UN Security Council draft resolution that demanded an immediate and unconditional ceasefire in the Gaza Strip.
Nearly 50,000 children in the West Bank also go to UNRWA schools.
On Oct. 28, the Israeli parliament voted to ban UNRWA, the main humanitarian aid provider in the Gaza Strip.
