Around 200 people demonstrated outside the UN compound in Gaza City, burning tyres and throwing stones.

"We are still homeless!" they chanted.

Some tried to storm the compound before police of the Islamist movement Hamas, the de facto power in Israeli-besieged Gaza, broke up the demonstration.

A UN statement condemned the assault, saying security forces had not provided enough security ahead of the planned protest.

"Despite repeated assurances, the security forces in Gaza did not take the necessary and timely measures to protect [the] compound," it said, adding the UN held Hamas "fully responsible" for the safety of its staff.

The incident came a day after Palestinian refugee agency UNRWA announced it can not afford to repair tens of thousands of homes damaged during the July-August war between Israel and Hamas because donors have failed to pay.

Some 100,000 people remain homeless since the 50-day conflict, which killed nearly 2,200 Palestinians and 73 people on the Israeli side.

UNRWA said cutting subsidies to displaced residents now renting alternative accommodation could force large numbers back to UN schools and centres which are already sheltering 12,000 people.

Reconstruction has barely begun, with experts saying it will take years even if Israel significantly eases its eight-year blockade on Gaza.

A Hamas official has warned the coastal territory could become a breeding ground for extremism unless promised reconstruction is accelerated. (+++++)