Staff at the United Nations agency for Palestinian refugees went on strike in the Gaza Strip on Monday to protest against job losses and US funding cuts.
The one-day strike closed more than 250 UNRWA schools in Gaza, as well as medical centres and food aid distribution points, the union said.
The United States has traditionally been UNRWA's largest funder, providing around $350 million (300 million euros) a year.
But President Donald Trump has cut all support, sparking a funding crisis.
More than 250 jobs have been cut in Gaza and the West Bank so far, while hundreds of full-time roles have become part-time.
The refugee agency's labour union is demanding the job cuts be reversed and its leaders say the strike could be the first of a number of measures.
A small protest took place outside the agency's Gaza headquarters.
"The strike comes in light of the (UNRWA) administration's lack of responsiveness to the demands of the employees' union and their insistence on not solving their problems," Amal al-Batsh, deputy head of the union, said in a statement.
UNRWA's spokesman Chris Gunness said the agency regretted the strike.
"We regret any action that negatively impacts the services we provide to refugees, particularly in a place like Gaza where after a more than decade of blockade they have suffered enough," he told AFP.
UNRWA says the funding deficit caused by the Trump administration's withdrawal of support is so severe cuts are unavoidable.
Around 13,000 people work for the agency in Gaza, where more than two-thirds of the roughly two million residents are eligible for aid.
UNRWA says more than 200,000 Palestinians attend its schools in the strip.