The main UN aid agency in the Gaza Strip said on Tuesday a lack of international funding had forced it to suspend payments to tens of thousands of Palestinians for repairs to homes damaged in last summer's war.

Sources in Hamas, which governs the Strip are fuming over the decision, which they say will turn Gaza into a ticking bomb that could explode at any moment. Hamas called on the international community to take responsibility in the Gaza Strip and ease the suffering of its inhabitants.

"People are literally sleeping amongst the rubble, children have died of hypothermia," Robert Turner, Gaza director of operations for the United Nations Relief and Works Agency (UNRWA), said in a statement.

"People are desperate and the international community cannot even provide the bare minimum – for example a repaired home in winter – let alone a lifting of the blockade, access to markets or freedom of movement," Turner said, adding that UNRWA urgently required $100 million in the first quarter of 20015 to repair minor damage to homes and for rental subsidies.

Turner said UNRWA received only $135 million of the $720 million pledged by donors to its cash assistance program for 96,000 refugee families whose homes were damaged or destroyed in the 50-day conflict between the Hamas Islamist movement and Israel.

"It is unclear why this funding has not been forthcoming," Turner said, without identifying the source of the shortfall. "While some funds remain available to begin the reconstruction of totally destroyed homes, the agency has exhausted all funding to support repairs and rental subsidies."

So far, he said, UNRWA has provided more than $77 million to 66,000 families to repair their homes or find temporary alternatives, but now due to a lack of funds the agency "has been forced to suspend its cash assistance program".

Little of the total $5.4 billion pledged for Gaza's reconstruction at a Cairo conference of international donors last October has reached the territory, and thousands of Palestinians have been sheltering in tents near destroyed homes.

Thousands more have been living in damaged buildings, using plastic sheeting to try to keep out the rain. Around 20,000 displaced are still being housed in UN-run schools.

Israel tightly monitors import of construction materials into the enclave, saying Hamas could use the supplies to rebuild cross-border tunnels through which militants attacked. Egypt and Israel maintain a Gaza blockade, with both countries citing security concerns for the restrictions.

The Israeli human rights group Gisha – Legal Center for Freedom of Movement, said that the rehabilitation plan for Gaza had been approved by Israel and by the Palestinian Authority and a mechanism was devised to allow materials to be delivered to the private sector while preventing such materials from reaching extremist groups. However, the plan has not met its goals. From the end of Operation Protective Edge in late December, 194,404 tons of construction materials had entered the Gaza Strip (34,570 tons through the mechanism), while an estimated, 5 million tons of construction materials are needed to repair the damage from the war and for the ongoing development of the Strip.

A great deal of the material coming into the Strip has reportedly leaked onto the black market. A sack of cement acquired through the mechanism reportedly costs 25 shekels (about $6.25) a sack of cement on the black market costs between 90 and 100 shekels.

Internal political fighting between Hamas and the Western-backed Palestinian Authority, which was to have overseen such shipments has also been a major factor in reconstruction delays.

Other Palestinian factions have also protested the decision to halt reconstruction payments, saying that it was hasty, would only increase the suffering of the Palestinians and could lead to escalation and renewed violence.

Some in the Palestinian Authority asked PA President Mahmoud Abbas to act immediately to implement the decision to establish an economic safety net by the Arab countries for the residents of Gaza, while the PA accused Hamas of not allowing the sovereign government to function in the Strop, which they say is what is preventing the entry of materials and the flow of money for reconstruction.