Ahmed Yousef, a senior Hamas official, speaking to Al Jazeera earlier, said the ties with Unrwa was "a strategic one" and admitted there were "some mistakes that have been committed by some people".

Call to lift blockade

Meanwhile on Monday, UN officials reiterated their call for Israel to lift the blockade on Gaza and open the crossings for urgent supplies to be sent in to the Palestinian territory.

"It is absolutely crucial that Israel allow the crossings to be opened"

Radhika Coomaraswamy, UN special envoy

"It is absolutely crucial that Israel allow the crossings to be opened and also expand the list of items that go in," Radhika Coomaraswamy, the UN special representative for children and armed conflict, told reporters following her recent visit to Gaza, the West Bank and southern Israel.

"At the moment less than 200 [aid] trucks are going through [the crossing points into Gaza]," she said.

"We need at least 400 just for the humanitarian needs and over 1,000 once reconstruction begins."

The UN also appealed for Israel to allow plastic bags and human rights textbooks into the Gaza Strip.

"We run out of plastic bags to distribute the food," John Ging, the Unrwa director of operations in Gaza, said in a video link on Monday, adding that the process of getting the plastic locally was "unreliable" and "very expensive".

Unrwa, which only provides assistance to Palestinians holding refugee status, plays a key role in distributing aid in Gaza by handing out food aid to some 900,000 people of out of a population of 1.5 million.