The UN says it is suspending all its food distribution centres in the Gaza Strip after protesters, angered by aid cutbacks, stormed one of its compounds.
The UN Relief and Works Agency (Unrwa) said the centres would stay closed until it received security assurances for its property and staff.
It said it was trying to mitigate the effects caused by cuts in cash payments to some of Gaza's poorest families.
Unrwa provides aid for an estimated 800,000 Palestinians in Gaza.
It runs dozens of schools and medical clinics and distributes food to many of the territory's 1.7 million residents, but says it is grappling with a huge budget deficit.
Correspondents say the suspension of food aid will cause more hardship for people in Gaza already hit by Israeli and Egyptian controls on its borders.
An Unrwa statement said the storming of its Gaza field office was "a dramatic and disturbing escalation in a series of demonstrations that have taken place over the past week".
"We fully understand the impact the decision to suspend cash assistance had on some of our beneficiaries," Robert Turner, head of the agency's Gaza operations, said in the statement.
"What happened today was completely unacceptable. The situation could very easily have resulted in serious injuries to Unrwa staff and to the demonstrators. This escalation, apparentlypre-planned, was unwarranted and unprecedented."
He added, "All relief and distribution centres will consequently remain closed until guarantees are given by all relevant groups that Unrwa operations can continue unhindered."
Sami Abu Zuhri, a spokesperson for Hamas which governs Gaza, said they condemned any violence against Unrwa but described the decision to close the food centres as "unjustified".
"When the administration of Unrwa asked the Palestinian security to intervene, they arrived and stopped the chaos. We are asking Unrwa to rethink their decision," he said.
Unrwa says financial support for its programmes to help Palestinian refugees hasn't kept up with the deepening poverty of those in need.
It says it is currently grappling with a deficit of more than $67m (£44m). — BBC