United Nations chief Ban Ki-moon has called for those responsible for bombing UN-run buildings and schools in Gaza to be held accountable following Israel’s 22-day onslaught in Gaza.

Clearly angry, the UN Secretary-General was speaking outside the still-smouldering main UN Relief and Works Agency compound in Gaza City, hit during shelling by Israeli artillery last Thursday, setting fire to the building and food aid stored inside.

Other UN buildings were hit during the fighting, and a number of Palestinian refugees allowed to take shelter by the UN inside its schools were killed.

“It is an outrageous and totally unacceptable attack on the United Nations,” said Mr Ban.

“There must be a full investigation, a full explanation to make sure it never happens again. There should be accountabilty through a proper judiciary system.”

The Israeli offensive ended last Sunday, leaving extensive damage in its wake.

Some 1,300 Palestinians were killed, and thousands more wounded. A sixth of the buildings in the overcrowded territory were reduced to rubble.

Israel lost three civilians hit by Hamas rocket fire in Israel and 10 soldiers were killed in action, including four by ‘friendly fire’.

“I have seen only a fraction of the destruction. This is shocking and alarming,” Mr Ban told an outdoor press conference.

“These are heartbreaking scenes I have seen and I am deeply aggrieved by what I have seen today.”

He condemned “excessive use” of force by Israel, as well as rockets fired by Hamas militants.

Israel apologised after the shelling of the UN relief compound but said that its forces had been responding to shooting from gunmen at the facility — a claim that UN officials have denied.

Mr Ban called for Palestinian reconciliation and said that the UN would work with any united Palestinian government to rebuild the Gaza Strip.

He is the most senior international official to visit Gaza since Hamas seized power in the Gaza Strip in June 2007.

The Hamas government is not internationally recognised, and Mr Ban is not scheduled to meet the group. Hamas held a rally outside the compound during Mr Ban’s visit, calling for international recognition of its government.

Meanwhile, Foreign Affairs Minister Michael Martin yesterday condemned Israel’s “disproportionate” attack in its invasion of Gaza.

However, calls for the withdrawal or expulsion of ambassadors as a result of the conflict were “misguided and counterproductive”, he added.