On his first visit to Gaza since the end of Israel's Operation Cast Lead, UN Secretary-General Ban Ki-moon called the ongoing siege "not sustainable" adding that the continued closure "is wrong."

More than a year after he spoke in front of the smoldering remains of the UN warehouse in Gaza City, hit by Israeli missiles during the December 2008-January 2009 war, Ban addressed Gazans in Khan Younis, saying they "are striving to provide for their families amid unacceptable, unsustainable conditions."

The Israeli siege of Gaza, Ban said, "causes unacceptable suffering of human beings," with half of the areas population, which is under the age of 18, suffering the most, a UN news brief quoted the official as saying.

"The policy is also counter-productive ... [and] prevents legitimate commerce and encourages smuggling. It undercuts moderates and empowers extremists."

Speaking of the UN housing and reconstruction projects recently okayed by Israel, Ban said that, "While I believe that this is a positive welcome step, I believe again we need far, far, much more," adding, "This is like a drop in a bucket of water."

Speaking in Moscow on Friday, Ban said the Israeli government had "just approved the very longstanding United Nations humanitarian project," which included water and sanitation projects, temporary schools and the completion of 150 housing units for Gazans.

"The Government of Israel has agreed to expand the list of imports to include aluminum for window frames. It’s vital now that these steps are speedily implemented. The needs in Gaza remains huge," Ban told reporters at the time.

Ban was received at the Erez crossing Sunday by 200 students and war amputees holding a series of banners asking the official to hold Israel to the standards of international law.

“We live in a place that Israel decided international law did not exist. With their warplanes and tanks, they rose above their commitments and the Geneva Conventions like they were just so much as ink on paper," a banner lining Salah Ad-Din Street said.

"We are addressing you today on behalf of those whose houses were demolished during Israel’s war on Gaza; they are still awaiting the reconstruction of their homes," a second banner read.

"We address you on behalf of more than 500 victims who died as a result of the crippling siege because they couldn’t travel abroad for treatment," read a third, "and on behalf of hundreds of other patients and those suffering on account of the siege."

The people of Gaza are "looking forward to freedom and justice," a final banner along the street read.